2D Histogram

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Hi,
I have a problem to create 2D histogram. I have two data sets: ISIs in ms (0-500 ms, 250 bin, 250 ms binsize; Vm -60- -45mV, 250 bin, 0.1mV binsize) I've tried the commands below:

•make/n=(250,250) myHist
•setscale x,0,500,myHist
•setscale y,-60,-45, myHist
JointHistogram(data1,data2,myHist) or Function JointHistogram(data1,data2,myHist)

but I have an error message. Can anyone help?
Thanks,
You need to post the JointHistogram function from http://www.igorexchange.com/node/1373 into your procedure window.

Having done that, I was able to successfully execute these commands:
Make /O /N=1000 xData = 500 * p/1000
Make /O /N=1000 yData = -60 + (15*p/1000)
Make /O /N=(250,250) myHist
SetScale x,0,500,myHist
SetScale y,-60,-45, myHist
JointHistogram(xData,yData,myHist)
NewImage myHist

June 11, 2012 at 05:56 pm - Permalink

Hi,

Yes, thank you very much. Meantime I have found my mistake in the function as well. It works fine in my case too and I got a nice contour plot. I have an other question. How can I normalise the matrix of the results of the 2D Histogram?
Also if I would like to represent the 'density' or the number of dots in each bins and I apply the contour plot how can I set values for the z axe and represent in 3D graph?

Thank you very much for your help,
Marti

June 12, 2012 at 03:14 am - Permalink

Marti wrote:
How can I normalise the matrix of the results of the 2D Histogram?

You have not defined what you mean by normalization. If you only want the output to sum to 1 then execute:
Variable sss=sum(matrix2d)
Duplicate/O matrix2d,normalized2d // never modify the original
normalized2d/=sss

Marti wrote:
Also if I would like to represent the 'density' or the number of dots in each bins and I apply the contour plot how can I set values for the z axe and represent in 3D graph?

You are not telling us what kind of a 3D graph you want to plot: do you want to plot a surface, a scatter or maybe some kind of a 3D bar chart?

A.G.
WaveMetrics, Inc.

June 12, 2012 at 01:05 pm - Permalink

Hi A.G.,
Thank you very much for your help, the normalization works fine.

I'm sorry if I wasn't enough precise, I meant the surface plot as a 3D graph. But you are right the 3D bar chart can be interesting as well.

Thanks,

June 13, 2012 at 02:55 am - Permalink

Hi A.G.

I managed to create the surface plot as well. Thanks!!!!

Marti

A.G.
WaveMetrics, Inc.[/quote]

June 13, 2012 at 03:49 am - Permalink

Marti,

Typically histograms are plotted in a bar-chart mode (although that is partly a matter of taste). AG was perhaps too modest to mention his Gizmo3DBarChart.ipf that comes with Igor, in the Wavemetrics Procedures:Gizmo Procedures folder.

If you don't care for the spacing between bars, then a surface plot will do. Be aware however that standard surface plots interpolate over the grid. If you want flat-topped bins of the histogram in a surface mode, AG had sent me the following procedure for converting to a parametric surface wave:
Function makeParametric(inWave)
    Wave inWave
    
    Variable rows=dimSize(inWave,0)
    Variable cols=dimSize(inWave,1)
    Variable i,j,val
    
    Make/N=(2*rows,2*cols,3)/O paramWave
    // fill the x-values
    Variable x0=dimOffset(inWave,0)
    Variable dx=dimDelta(inWave,0)
    Variable curx=x0
    for(i=0;i<rows;i+=1)
        paramWave[2*i][][0]=curX
        paramWave[2*i+1][][0]=curX+dx
        curX+=dx
    endfor
    
    // fill the y-values
    Variable y0=dimOffset(inWave,1)
    Variable dy=dimDelta(inWave,1)
    Variable cury=y0
    for(i=0;i<cols;i+=1)
        paramWave[][2*i][1]=curY
        paramWave[][2*i+1][1]=curY+dy
        curY+=dy
    endfor
    
    // fill the z-values
    for(i=0;i<rows;i+=1)
        for(j=0;j<cols;j+=1)
            val=inWave[i][j]
            paramWave[2*i][2*j][2]=val
            paramWave[2*i+1][2*j][2]=val
            paramWave[2*i][2*j+1][2]=val
            paramWave[2*i+1][2*j+1][2]=val
        endfor
    endfor
    
End

June 13, 2012 at 04:36 am - Permalink