Re: Random ROI / results selection for measurement

Posted by Tiago Ferreira-2 on Dec 04, 2009; 4:07pm
URL: http://imagej.273.s1.nabble.com/Random-ROI-results-selection-for-measurement-tp3689378p3689379.html

> I've searched through the archives, and I haven't find a clue about this:
> Is there an easy/elegant way to random select x ROIs for measurement? Eg. I
> have around 230 ROIs, but I need only 200 results for the statistical
> analysis.
> Regards
>
> Ákos

Dear Ákos,
this issue has already been discussed here. Have a look at:
<https://list.nih.gov/cgi-bin/wa?A2=ind0902&L=IMAGEJ&P=R27945&I=-3>

As Curtis suggested probably the best way to do it is to use Fisher Yates
shuffle: <http://en.wikipedia.org/wiki/Fisher-Yates_shuffle>.

It could be something like the lines below but have a look at Curtis suggestion

// ---  

k=0; n=roiManager("count"); rois=newArray(n);

for(i=0;i<n;i++)
    rois[i]=k++;

myFisherYates(rois);

sample = getNumber("Size of Sample?", n);

count=1;
for(i=0;i<sample;i++) {
    roiManager("select", rois[i]);
    roiManager("measure");
    print(count++ +"/"+sample+" : Measured ROI:  "+rois[i]);
   
}

function myFisherYates(array) {
    if(array.length!=0) {
        for (i=0;i<array.length ;i++) {
            j = floor(random()*(i+1));
            temp1 = array[i]; temp2 = array[j];
            array[i] = temp2; array[j] = temp1;
        }
    }
}