How to select Image sequencing style in PIVlab v2.38

[Dinesh Parthasarathy]

Hi Dr. William,

I am trying to perform the analysis by uploading the video (new feature in v2.38) and specifying the frames of interest.

While we get to choose between time-resolved ([A+B],[B+C],[C+D]...) and Pairwise ([A+B],[C+D],[E+F]...) when images are being imported, I'm unable to locate the option to perform this, while uploading a video and carrying out the analysis.

Also, the analysis which I performed with the video uploaded gave only 10-15 points in the velocity scatter plot (Image attached). I'm uncertain why this is happening.

I can share the video (about 7GB) if you would be able to take a look at it.

Settings used:

FFT with two passes; 128px and 64px.

Thanks and Warm Regards,

[William Thielicke]

Hi, please share the video, I'll check it.

The sequencing style in videos is always time-resolved. But you can skip frames if you recorded with a frame rate that is too high. Does that not make sense?

[Dinesh Parthasarathy]

I'm attaching the video here. Thanks again for taking the time, William!

Totally makes sense to skip frames with higher fps, but the temporal resolution of my video is 1 frame/sec. Hence, I was a little confused.

Best,

Dinesh

[William Thielicke]

Hi, the analysis worked for me. If you create scatter plots in the Vector validation menu, then not every single vector is plotted. The points are randomly selected from the full dataset, because otherwise Matlab used to freeze in the past.

You could remove the limit in PIVlab_GUI.m:

if size(datau,2)>20000 %more than 20000 value pairs are too slow in scatterplot.

pos=unique(ceil(rand(21000,1)*(size(datau,2)-1))); %select random entries...

scatter(gca,datau(pos),datav(pos), 'b.'); %.. and plot them

set(gca,'Yaxislocation','right','layer','top');

else

scatter(gca,datau,datav, 'b.');

set(gca,'Yaxislocation','right','layer','top');

end