Flot Reference -------------- Consider a call to the plot function: var plot = $.plot(placeholder, data, options) The placeholder is a jQuery object or DOM element or jQuery expression that the plot will be put into. This placeholder needs to have its width and height set as explained in the README (go read that now if you haven't, it's short). The plot will modify some properties of the placeholder so it's recommended you simply pass in a div that you don't use for anything else. Make sure you check any fancy styling you apply to the div, e.g. background images have been reported to be a problem on IE 7. The format of the data is documented below, as is the available options. The "plot" object returned has some methods you can call. These are documented separately below. Note that in general Flot gives no guarantees if you change any of the objects you pass in to the plot function or get out of it since they're not necessarily deep-copied. Data Format ----------- The data is an array of data series: [ series1, series2, ... ] A series can either be raw data or an object with properties. The raw data format is an array of points: [ [x1, y1], [x2, y2], ... ] E.g. [ [1, 3], [2, 14.01], [3.5, 3.14] ] Note that to simplify the internal logic in Flot both the x and y values must be numbers, even if specifying time series (see below for how to do this). This is a common problem because you might retrieve data from the database and serialize them directly to JSON without noticing the wrong type. If you're getting mysterious errors, double check that you're inputting numbers and not strings. If a null is specified as a point or if one of the coordinates is null or couldn't be converted to a number, the point is ignored when drawing. As a special case, a null value for lines is interpreted as a line segment end, i.e. the point before and after the null value are not connected. Lines and points take two coordinates. For bars, you can specify a third coordinate which is the bottom of the bar (defaults to 0). The format of a single series object is as follows: { color: color or number data: rawdata label: string lines: specific lines options bars: specific bars options points: specific points options threshold: specific threshold options xaxis: 1 or 2 yaxis: 1 or 2 clickable: boolean hoverable: boolean shadowSize: number } You don't have to specify any of them except the data, the rest are options that will get default values. Typically you'd only specify label and data, like this: { label: "y = 3", data: [[0, 3], [10, 3]] } The label is used for the legend, if you don't specify one, the series will not show up in the legend. If you don't specify color, the series will get a color from the auto-generated colors. The color is either a CSS color specification (like "rgb(255, 100, 123)") or an integer that specifies which of auto-generated colors to select, e.g. 0 will get color no. 0, etc. The latter is mostly useful if you let the user add and remove series, in which case you can hard-code the color index to prevent the colors from jumping around between the series. The "xaxis" and "yaxis" options specify which axis to use, specify 2 to get the secondary axis (x axis at top or y axis to the right). E.g., you can use this to make a dual axis plot by specifying { yaxis: 2 } for one data series. "clickable" and "hoverable" can be set to false to disable interactivity for specific series if interactivity is turned on in plot, see below. The rest of the options are all documented below as they are the same as the default options passed in via the options parameter in the plot commmand. When you specify them for a specific data series, they will override the default options for the plot for that data series. Here's a complete example of a simple data specification: [ { label: "Foo", data: [ [10, 1], [17, -14], [30, 5] ] }, { label: "Bar", data: [ [11, 13], [19, 11], [30, -7] ] } ] Plot Options ------------ All options are completely optional. They are documented individually below, to change them you just specify them in an object, e.g. var options = { lines: { show: true }, points: { show: true } }; $.plot(placeholder, data, options); Customizing the legend ====================== legend: { show: boolean labelFormatter: null or (fn: string, series object -> string) labelBoxBorderColor: color noColumns: number position: "ne" or "nw" or "se" or "sw" margin: number of pixels or [x margin, y margin] backgroundColor: null or color backgroundOpacity: number between 0 and 1 container: null or jQuery object/DOM element/jQuery expression } The legend is generated as a table with the data series labels and small label boxes with the color of the series. If you want to format the labels in some way, e.g. make them to links, you can pass in a function for "labelFormatter". Here's an example that makes them clickable: labelFormatter: function(label, series) { // series is the series object for the label return '' + label + ''; } "noColumns" is the number of columns to divide the legend table into. "position" specifies the overall placement of the legend within the plot (top-right, top-left, etc.) and margin the distance to the plot edge (this can be either a number or an array of two numbers like [x, y]). "backgroundColor" and "backgroundOpacity" specifies the background. The default is a partly transparent auto-detected background. If you want the legend to appear somewhere else in the DOM, you can specify "container" as a jQuery object/expression to put the legend table into. The "position" and "margin" etc. options will then be ignored. Note that Flot will overwrite the contents of the container. Most of the above settings do not apply Customizing the axes ==================== xaxis, yaxis, x2axis, y2axis: { mode: null or "time" min: null or number max: null or number autoscaleMargin: null or number labelWidth: null or number labelHeight: null or number ticks: null or number or ticks array or (fn: range -> ticks array) tickSize: number or array minTickSize: number or array tickFormatter: (fn: number, object -> string) or string tickDecimals: null or number } All axes have the same kind of options. The "mode" option determines how the data is interpreted, the default of null means as decimal numbers. Use "time" for time series data, see the next section. The options "min"/"max" are the precise minimum/maximum value on the scale. If you don't specify either of them, a value will automatically be chosen based on the minimum/maximum data values. The "autoscaleMargin" is a bit esoteric: it's the fraction of margin that the scaling algorithm will add to avoid that the outermost points ends up on the grid border. Note that this margin is only applied when a min or max value is not explicitly set. If a margin is specified, the plot will furthermore extend the axis end-point to the nearest whole tick. The default value is "null" for the x axis and 0.02 for the y axis which seems appropriate for most cases. "labelWidth" and "labelHeight" specifies the maximum size of the tick labels in pixels. They're useful in case you need to align several plots. The rest of the options deal with the ticks. If you don't specify any ticks, a tick generator algorithm will make some for you. The algorithm has two passes. It first estimates how many ticks would be reasonable and uses this number to compute a nice round tick interval size. Then it generates the ticks. You can specify how many ticks the algorithm aims for by setting "ticks" to a number. The algorithm always tries to generate reasonably round tick values so even if you ask for three ticks, you might get five if that fits better with the rounding. If you don't want any ticks at all, set "ticks" to 0 or an empty array. Another option is to skip the rounding part and directly set the tick interval size with "tickSize". If you set it to 2, you'll get ticks at 2, 4, 6, etc. Alternatively, you can specify that you just don't want ticks at a size less than a specific tick size with "minTickSize". Note that for time series, the format is an array like [2, "month"], see the next section. If you want to completely override the tick algorithm, you can specify an array for "ticks", either like this: ticks: [0, 1.2, 2.4] Or like this where the labels are also customized: ticks: [[0, "zero"], [1.2, "one mark"], [2.4, "two marks"]] You can mix the two if you like. For extra flexibility you can specify a function as the "ticks" parameter. The function will be called with an object with the axis min and max and should return a ticks array. Here's a simplistic tick generator that spits out intervals of pi, suitable for use on the x axis for trigonometric functions: function piTickGenerator(axis) { var res = [], i = Math.floor(axis.min / Math.PI); do { var v = i * Math.PI; res.push([v, i + "\u03c0"]); ++i; } while (v < axis.max); return res; } You can control how the ticks look like with "tickDecimals", the number of decimals to display (default is auto-detected). Alternatively, for ultimate control over how ticks look like you can provide a function to "tickFormatter". The function is passed two parameters, the tick value and an "axis" object with information, and should return a string. The default formatter looks like this: function formatter(val, axis) { return val.toFixed(axis.tickDecimals); } The axis object has "min" and "max" with the range of the axis, "tickDecimals" with the number of decimals to round the value to and "tickSize" with the size of the interval between ticks as calculated by the automatic axis scaling algorithm (or specified by you). Here's an example of a custom formatter: function suffixFormatter(val, axis) { if (val > 1000000) return (val / 1000000).toFixed(axis.tickDecimals) + " MB"; else if (val > 1000) return (val / 1000).toFixed(axis.tickDecimals) + " kB"; else return val.toFixed(axis.tickDecimals) + " B"; } Time series data ================ Time series are a bit more difficult than scalar data because calendars don't follow a simple base 10 system. For many cases, Flot abstracts most of this away, but it can still be a bit difficult to get the data into Flot. So we'll first discuss the data format. The time series support in Flot is based on Javascript timestamps, i.e. everywhere a time value is expected or handed over, a Javascript timestamp number is used. This is a number, not a Date object. A Javascript timestamp is the number of milliseconds since January 1, 1970 00:00:00 UTC. This is almost the same as Unix timestamps, except it's in milliseconds, so remember to multiply by 1000! You can see a timestamp like this alert((new Date()).getTime()) Normally you want the timestamps to be displayed according to a certain time zone, usually the time zone in which the data has been produced. However, Flot always displays timestamps according to UTC. It has to as the only alternative with core Javascript is to interpret the timestamps according to the time zone that the visitor is in, which means that the ticks will shift unpredictably with the time zone and daylight savings of each visitor. So given that there's no good support for custom time zones in Javascript, you'll have to take care of this server-side. The easiest way to think about it is to pretend that the data production time zone is UTC, even if it isn't. So if you have a datapoint at 2002-02-20 08:00, you can generate a timestamp for eight o'clock UTC even if it really happened eight o'clock UTC+0200. In PHP you can get an appropriate timestamp with 'strtotime("2002-02-20 UTC") * 1000', in Python with 'calendar.timegm(datetime_object.timetuple()) * 1000', in .NET with something like: public static int GetJavascriptTimestamp(System.DateTime input) { System.TimeSpan span = new System.TimeSpan(System.DateTime.Parse("1/1/1970").Ticks); System.DateTime time = input.Subtract(span); return (long)(time.Ticks / 10000); } Javascript also has some support for parsing date strings, so it is possible to generate the timestamps manually client-side. If you've already got the real UTC timestamp, it's too late to use the pretend trick described above. But you can fix up the timestamps by adding the time zone offset, e.g. for UTC+0200 you would add 2 hours to the UTC timestamp you got. Then it'll look right on the plot. Most programming environments have some means of getting the timezone offset for a specific date (note that you need to get the offset for each individual timestamp to account for daylight savings). Once you've gotten the timestamps into the data and specified "time" as the axis mode, Flot will automatically generate relevant ticks and format them. As always, you can tweak the ticks via the "ticks" option - just remember that the values should be timestamps (numbers), not Date objects. Tick generation and formatting can also be controlled separately through the following axis options: minTickSize: array timeformat: null or format string monthNames: null or array of size 12 of strings Here "timeformat" is a format string to use. You might use it like this: xaxis: { mode: "time" timeformat: "%y/%m/%d" } This will result in tick labels like "2000/12/24". The following specifiers are supported %h': hours %H': hours (left-padded with a zero) %M': minutes (left-padded with a zero) %S': seconds (left-padded with a zero) %d': day of month (1-31) %m': month (1-12) %y': year (four digits) %b': month name (customizable) You can customize the month names with the "monthNames" option. For instance, for Danish you might specify: monthNames: ["jan", "feb", "mar", "apr", "maj", "jun", "jul", "aug", "sep", "okt", "nov", "dec"] The format string and month names are used by a very simple built-in format function that takes a date object, a format string (and optionally an array of month names) and returns the formatted string. If needed, you can access it as $.plot.formatDate(date, formatstring, monthNames) or even replace it with another more advanced function from a date library if you're feeling adventurous. If everything else fails, you can control the formatting by specifying a custom tick formatter function as usual. Here's a simple example which will format December 24 as 24/12: tickFormatter: function (val, axis) { var d = new Date(val); return d.getUTCDate() + "/" + (d.getUTCMonth() + 1); } Note that for the time mode "tickSize" and "minTickSize" are a bit special in that they are arrays on the form "[value, unit]" where unit is one of "second", "minute", "hour", "day", "month" and "year". So you can specify minTickSize: [1, "month"] to get a tick interval size of at least 1 month and correspondingly, if axis.tickSize is [2, "day"] in the tick formatter, the ticks have been produced with two days in-between. Customizing the data series =========================== lines, points, bars: { show: boolean lineWidth: number fill: boolean or number fillColor: null or color/gradient } points: { radius: number } bars: { barWidth: number align: "left" or "center" horizontal: boolean } lines: { steps: boolean } colors: [ color1, color2, ... ] shadowSize: number threshold: { below: number color: color } The most important options are "lines", "points" and "bars" that specifies whether and how lines, points and bars should be shown for each data series. In case you don't specify anything at all, Flot will default to showing lines (you can turn this off with lines: { show: false}). You can specify the various types independently of each other, and Flot will happily draw each of them in turn, e.g. var options = { lines: { show: true, fill: true, fillColor: "rgba(255, 255, 255, 0.8)" }, points: { show: true, fill: false } }; "lineWidth" is the thickness of the line or outline in pixels. You can set it to 0 to prevent a line or outline from being drawn; this will also hide the shadow. "fill" is whether the shape should be filled. For lines, this produces area graphs. You can use "fillColor" to specify the color of the fill. If "fillColor" evaluates to false (default for everything except points which are filled with white), the fill color is auto-set to the color of the data series. You can adjust the opacity of the fill by setting fill to a number between 0 (fully transparent) and 1 (fully opaque). For bars, fillColor can be a gradient, see the gradient documentation below. "barWidth" is the width of the bars in units of the x axis, contrary to most other measures that are specified in pixels. For instance, for time series the unit is milliseconds so 24 * 60 * 60 * 1000 produces bars with the width of a day. "align" specifies whether a bar should be left-aligned (default) or centered on top of the value it represents. When "horizontal" is on, the bars are drawn horizontally, i.e. from the y axis instead of the x axis; note that the bar end points are still defined in the same way so you'll probably want to swap the coordinates if you've been plotting vertical bars first. For lines, "steps" specifies whether two adjacent data points are connected with a straight (possibly diagonal) line or with first a horizontal and then a vertical line. The "colors" array specifies a default color theme to get colors for the data series from. You can specify as many colors as you like, like this: colors: ["#d18b2c", "#dba255", "#919733"] If there are more data series than colors, Flot will try to generate extra colors by lightening and darkening colors in the theme. "shadowSize" is the default size of shadows in pixels. Set it to 0 to remove shadows. "threshold" specifies that the data points below "below" should be drawn with the specified color. This makes it easy to mark points below 0, e.g. for budget data. Customizing the grid ==================== grid: { color: color backgroundColor: color/gradient or null tickColor: color labelMargin: number markings: array of markings or (fn: axes -> array of markings) borderWidth: number borderColor: color or null clickable: boolean hoverable: boolean autoHighlight: boolean mouseActiveRadius: number } The grid is the thing with the axes and a number of ticks. "color" is the color of the grid itself whereas "backgroundColor" specifies the background color inside the grid area. The default value of null means that the background is transparent. You can also set a gradient, see the gradient documentation below. "tickColor" is the color of the ticks and "labelMargin" is the spacing between tick labels and the grid. Note that you can style the tick labels with CSS, e.g. to change the color. They have class "tickLabel". "borderWidth" is the width of the border around the plot. Set it to 0 to disable the border. You can also set "borderColor" if you want the border to have a different color than the grid lines. "markings" is used to draw simple lines and rectangular areas in the background of the plot. You can either specify an array of ranges on the form { xaxis: { from, to }, yaxis: { from, to } } (secondary axis coordinates with x2axis/y2axis) or with a function that returns such an array given the axes for the plot in an object as the first parameter. You can set the color of markings by specifying "color" in the ranges object. Here's an example array: markings: [ { xaxis: { from: 0, to: 2 }, yaxis: { from: 10, to: 10 }, color: "#bb0000" }, ... ] If you leave out one of the values, that value is assumed to go to the border of the plot. So for example if you only specify { xaxis: { from: 0, to: 2 } } it means an area that extends from the top to the bottom of the plot in the x range 0-2. A line is drawn if from and to are the same, e.g. markings: [ { yaxis: { from: 1, to: 1 } }, ... ] would draw a line parallel to the x axis at y = 1. You can control the line width with "lineWidth" in the ranges objects. An example function might look like this: markings: function (axes) { var markings = []; for (var x = Math.floor(axes.xaxis.min); x < axes.xaxis.max; x += 2) markings.push({ xaxis: { from: x, to: x + 1 } }); return markings; } If you set "clickable" to true, the plot will listen for click events on the plot area and fire a "plotclick" event on the placeholder with a position and a nearby data item object as parameters. The coordinates are available both in the unit of the axes (not in pixels) and in global screen coordinates. Likewise, if you set "hoverable" to true, the plot will listen for mouse move events on the plot area and fire a "plothover" event with the same parameters as the "plotclick" event. If "autoHighlight" is true (the default), nearby data items are highlighted automatically. If needed, you can disable highlighting and control it yourself with the highlight/unhighlight plot methods described elsewhere. You can use "plotclick" and "plothover" events like this: $.plot($("#placeholder"), [ d ], { grid: { clickable: true } }); $("#placeholder").bind("plotclick", function (event, pos, item) { alert("You clicked at " + pos.x + ", " + pos.y); // secondary axis coordinates if present are in pos.x2, pos.y2, // if you need global screen coordinates, they are pos.pageX, pos.pageY if (item) { highlight(item.series, item.datapoint); alert("You clicked a point!"); } }); The item object in this example is either null or a nearby object on the form: item: { datapoint: the point as you specified it in the data, e.g. [0, 2] dataIndex: the index of the point in the data array series: the series object seriesIndex: the index of the series pageX, pageY: the global screen coordinates of the point } For instance, if you have specified the data like this $.plot($("#placeholder"), [ { label: "Foo", data: [[0, 10], [7, 3]] } ], ...); and the mouse is near the point (7, 3), "datapoint" is the [7, 3] we specified, "dataIndex" will be 1, "series" is a normalized series object with among other things the "Foo" label in series.label and the color in series.color, and "seriesIndex" is 0. If you use the above events to update some other information and want to clear out that info in case the mouse goes away, you'll probably also need to listen to "mouseout" events on the placeholder div. "mouseActiveRadius" specifies how far the mouse can be from an item and still activate it. If there are two or more points within this radius, Flot chooses the closest item. For bars, the top-most bar (from the latest specified data series) is chosen. If you want to disable interactivity for a specific data series, you can set "hoverable" and "clickable" to false in the options for that series, like this { data: [...], label: "Foo", clickable: false }. Customizing the selection ========================= selection: { mode: null or "x" or "y" or "xy", color: color } You enable selection support by setting the mode to one of "x", "y" or "xy". In "x" mode, the user will only be able to specify the x range, similarly for "y" mode. For "xy", the selection becomes a rectangle where both ranges can be specified. "color" is color of the selection. When selection support is enabled, a "plotselected" event will be emitted on the DOM element you passed into the plot function. The event handler gets one extra parameter with the ranges selected on the axes, like this: placeholder.bind("plotselected", function(event, ranges) { alert("You selected " + ranges.xaxis.from + " to " + ranges.xaxis.to) // similar for yaxis, secondary axes are in x2axis // and y2axis if present }); The "plotselected" event is only fired when the user has finished making the selection. A "plotselecting" event is fired during the process with the same parameters as the "plotselected" event, in case you want to know what's happening while it's happening, A "plotunselected" event with no arguments is emitted when the user clicks the mouse to remove the selection. Customizing the crosshair ========================= crosshair: { mode: null or "x" or "y" or "xy" color: color } You can enable crosshairs, thin lines, that follow the mouse by setting the mode to one of "x", "y" or "xy". The "x" mode enables a vertical crosshair that lets you trace the values on the x axis, "y" enables a horizontal crosshair and "xy" enables them both. Specifying gradients ==================== A gradient is specified like this: { colors: [ color1, color2, ... ] } For instance, you might specify a background on the grid going from black to gray like this: grid: { backgroundColor: { colors: ["#000", "#999"] } } For the series you can specify the gradient as an object that specifies the scaling of the brightness and the opacity of the series color, e.g. { colors: [{ opacity: 0.8 }, { brightness: 0.6, opacity: 0.8 } ] where the first color simply has its alpha scaled, whereas the second is also darkened. Flot currently only supports vertical gradients drawn from top to bottom because that's what works with IE. Plot Methods ------------ The Plot object returned from the plot function has some methods you can call: - setSelection(ranges, preventEvent) Set the selection rectangle. The passed in ranges is on the same form as returned in the "plotselected" event. If the selection mode is "x", you should put in either an xaxis (or x2axis) object, if the mode is "y" you need to put in an yaxis (or y2axis) object and both xaxis/x2axis and yaxis/y2axis if the selection mode is "xy", like this: setSelection({ xaxis: { from: 0, to: 10 }, yaxis: { from: 40, to: 60 } }); setSelection will trigger the "plotselected" event when called. If you don't want that to happen, e.g. if you're inside a "plotselected" handler, pass true as the second parameter. - clearSelection(preventEvent) Clear the selection rectangle. Pass in true to avoid getting a "plotunselected" event. - setCrosshair(pos) Set the position of the crosshair. Note that this is cleared if the user moves the mouse. "pos" should be on the form { x: xpos, y: ypos } (or x2 and y2 if you're using the secondary axes), which is coincidentally the same format as what you get from a "plothover" event. If "pos" is null, the crosshair is cleared. - clearCrosshair() Clear the crosshair. - highlight(series, datapoint) Highlight a specific datapoint in the data series. You can either specify the actual objects, e.g. if you got them from a "plotclick" event, or you can specify the indices, e.g. highlight(1, 3) to highlight the fourth point in the second series. - unhighlight(series, datapoint) Remove the highlighting of the point, same parameters as highlight. - setData(data) You can use this to reset the data used. Note that axis scaling, ticks, legend etc. will not be recomputed (use setupGrid() to do that). You'll probably want to call draw() afterwards. You can use this function to speed up redrawing a plot if you know that the axes won't change. Put in the new data with setData(newdata) and call draw() afterwards, and you're good to go. - setupGrid() Recalculate and set axis scaling, ticks, legend etc. Note that because of the drawing model of the canvas, this function will immediately redraw (actually reinsert in the DOM) the labels and the legend, but not the actual tick lines because they're drawn on the canvas. You need to call draw() to get the canvas redrawn. - draw() Redraws the canvas. There are also some members that let you peek inside the internal workings of Flot which in some cases is useful. Note that if you change something in the objects returned, you're changing the objects used by Flot to keep track of its state, so be careful. - getData() Returns an array of the data series currently used on normalized form with missing settings filled in according to the global options. So for instance to find out what color Flot has assigned to the data series, you could do this: var series = plot.getData(); for (var i = 0; i < series.length; ++i) alert(series[i].color); - getAxes() Gets an object with the axes settings as { xaxis, yaxis, x2axis, y2axis }. Various things are stuffed inside an axis object, e.g. you could use getAxes().xaxis.ticks to find out what the ticks are for the xaxis. - getCanvas() Returns the canvas used for drawing in case you need to hack on it yourself. You'll probably need to get the plot offset too. - getPlotOffset() Gets the offset that the grid has within the canvas as an object with distances from the canvas edges as "left", "right", "top", "bottom". I.e., if you draw a circle on the canvas with the center placed at (left, top), its center will be at the top-most, left corner of the grid.