DSPLOT - downsampled plot

This function creates a downsampled plot to improve the speed of exploration (zoom, pan)

Description

This version of "plot" will allow you to visualize data that has very large number of elements. Plotting large data set makes your graphics sluggish, but most times you don't need all of the information displayed in the plot. Your screen only has so many pixels, and your eyes won't be able to detect any information not captured on the screen.

This function will downsample the data and plot only a subset of the data, thus improving the memory requirement. When the plot is zoomed in, more information gets displayed. Some work is done to make sure that outliers are captured.

Syntax:
 dsplot(x, y)
 dsplot(y)
 dsplot(x, y, numpoints)

Example:
 x =linspace(0, 2*pi, 1000000);
 y1=sin(x)+.02*cos(200*x)+0.001*sin(2000*x)+0.0001*cos(20000*x);
 dsplot(x,y1);

• MATLAB release: MATLAB 7.4 (R2007a)
• Other requirements: Only works for R2006b or later. It uses the zoom/pan customization feature which became available in R2006b.

[Joacim Rådstam]

Excellent function!
I often plot time series with more than 2 million samples and this function makes the plot so much faster to zoom and pan in. Also the maximizing and minimizing of the figure window is much faster.

[Rob C]

Looks very useful but am unable to run any of your examples. When I try this results:

??? One or more output arguments not assigned during call to 'C:\MATLAB701a\toolbox\matlab\graph2d\zoom.m (zoom)'.

Error in ==> dsplot at 94
hZoom = zoom(hFig);

Any ideas?

[Jiro Doke]

Rob,
I'm sorry to say that it is not designed to work with MATLAB 7.01, as mentioned in "Other Requirements". This tool only works because it uses a new feature that became available in R2006b (MATLAB 7.3). I've thought about trying to make this usable in earlier versions, but it would be more clunky and won't be able to make use of the built in zoom/pan features.

[Scott Miller]

 

[Kai]

Great! This function saved me. Large data plots run like hell with it! But I was missing the possibility to specify figure or axes handles to plot into.

[Joseph Kirk]

This is an excellent function to have. Good work. Have you considered writing code to do something similar for other plotting functions such as IMAGESC for example?

[M. A. Hopcroft]

Really useful! Thanks for sharing!

[Yuval Cohen]

You should also look at 'tplot'
It uses minimum and maximum rather than resample and runs much faster.

[Hoi Wong]

The function is great, but I'd really love to use it in subplots. Any chance to add support to subplots?

It'd be tricky to tell whether the plot is downsampled or true representation without changing the figure title. One way I can think of is to set the 'Color' property of the subplot axesHandle to very light yellow for downsampled display.

[Hoi Wong]

Oh....one more thing. I put NaNs in my signal so it wouldn't plot, but turns out it confuses dsplot's outlier search routine. Any good ways to get around that?