How to save (preserve) the zoom state of flot graphs on Update with AJAX

I have a simple application which polls database for data every minute. When new data is fetched, I am updating the graph using ajax. However, whenever I update the graph (re-plot it with new values adde开发者_开发百科d to plot data) the current state of zoom is lost. Before updating the graph, I want to preserve the latest zoom position. After updating the graph, I want to zoom the graph to its saved position. This is important because re-zooming every minute is irritating. Is this possible?

I tried this answer from Ozan and I couldn't get the block for copying the zoom to work so I just used plot.getOptions() and used that to draw the graph. Like this:

var oldOptions = plot.getOptions();
plot = $.plot($("#graph"), data, oldOptions);

This way you can dynamically change your view and the auto-update will update without changing your view.

Here is the answer by Joshua Varner 1

When you get your new data before you re plot get the current zoom and add it to the options on update.

// Get the current zoom
var zoom = plot.getAxes();

// Add the zoom to standard options
var zoomed = {};
$.extend(zoomed,options);
zoomed.xaxis.min = zoom.xaxis.min;
zoomed.xaxis.max = zoom.xaxis.max;
zoomed.yaxis.min = zoom.yaxis.min;
zoomed.yaxis.max = zoom.yaxis.max;

// draw/save the plot
plot = $.plot($("#graph"), d, zoomed);

You should get the information about the state of the current axes, merge it with your initial options and than provide them to the new plot.

// Deep copy of the options object so that we can keep it unchanged
// for when we don't want to preserve the zoom.
var copyOptions = $.extend(true, {}, options);

if (plot != null && preserveZoom) {
    // There might be more than one Y axis
    var zoomY = plot.getYAxes();

    for (var i = 0; i < zoomY.length; i++) {
        copyOptions.yaxes[i].min = zoomY[i].min;
        copyOptions.yaxes[i].max = zoomY[i].max;
    }

    // Considering only one X axis, in case of more than one
    // you should use the same method as for the Y axis.
    copyOptions.xaxis.min = plot.getXAxes()[0].min;
    copyOptions.xaxis.max = plot.getXAxes()[0].max;
}

plot = $.plot("#placeholder", data, copyOptions);