ROI selection

[Dennet02]

Hello, I really need help, so I have an image in which I must randomly select 50 cell nuclei, I already have all the image nuclei in my ROI manager, and I only want to select 50 of those, how can I do it?

[hansenjn]

Hello, you could realize that with an ImageJ macro.
Here is an example code.
Run this macro after you have all the ROIs in the ROI manager, and only 50 randomly selected ROIs will remain. Note, that this will give you a random selection of 50 ROIs that is different everytime you run the code.

// We need to know how many ROIs there are in total
nrOfRois = roiManager("count");

// Now we create an empty list of 50 numbers
randomNumbers = newArray(50);

// We fill this list with random numbers between 0 and nrOfRois
for (i = 0; i < 50; i++) {
	randomNumbers [i] = round(random * (nrOfRois-1.0));
	print("Selected ROI with index " + randomNumbers [i] + " to be kept.");
}

// Now we shuffle through all ROIs in the ROI manager ... 
for(i = nrOfRois-1; i >= 0; i --){
	keep = false;
	// ... and check whether each ROI is in the list of 50 random numbers
	for(j = 0; j < 50; j++){
		if(randomNumbers [j] == i){
			keep = true;
			break;
		}
	}
	// .. if it is not in the list, we delete the specific ROI
	if(keep == false){
		roiManager("select", i);
		roiManager("delete");
	}
}

To run this macro code in FIJI, go to Plugins > New > Macro. Then paste the Macro code I wrote above into the empty macro and click the Run button.

[Dennet02]

Thank you so much, it solved it

[Whistleblowe]

Hello, I really need help, so I have an image in which I must randomly select 50 cell nuclei, I already have all the image nuclei in my ROI manager, and I only want to select 50 of those, how can I do it?