How to import data to produce velocity image data

Attached to this post is the data file, and I need help achieving these objectives:

• Import SRAS_freq.txt and produce a velocity image of the data.
• You will need to separate the x and y and frequency information from the loaded array.
• The x and y axis spacing is different so the image is not square even though there are 200x200 data points, you should take this into account when creating the images.
• The Acoustic wavelength used for the scan was 24 microns.

I am unaware on how to start this and possible technqiues to use. How would I approach this? all possible avenues are welcome.

Many Thanks to all

[Jacob Wood]

Hi James,

What have you tried? Have you been able to import the data into Matlab? It looks to be nicely delimited, so readmatrix() might be a nice place to start: https://www.mathworks.com/help/matlab/ref/readmatrix.html

After the data is in Matlab what equations do you have available to produce a "velocity image"?

[Star Strider]

The data are gridded, so reading it and creating the matrices are straightforward:

D = load('SRAS_freq.txt');
[~,frm] = unique(D(:,2));
dfrm = mean(diff(frm));
D1 = reshape(D(:,1), dfrm, []);
D2 = reshape(D(:,2), dfrm, []);
D3 = reshape(D(:,3), dfrm, []);

Beyond that, I have no idea what you are doing.

[James Adams]

Hey Star,

it seems when i run the code, there is an error that comes up. For some reason Matlab cannot read the first line of code. Any ideas on how to rectify this?

Thank you

James

[Star Strider]

What is MATLAB apparently not able tto read?

[chengyi li]

Hi James, have you figure out about this questions?

I have the same problem for my coursework and I don't quite understand the concept 'velocity image'. what figures are expected and where is the concept (The Acoustic wavelength used for the scan was 24 microns.) used?

Thank you!!

[James Adams]

Hey,

I haven’t found the answer to this. Do you know how to do it?

Regards

James

[Ratty419]

Hello James, were you able to fix this? Can I see your final output?

Answer 1

[Image Analyst]

Try this:

D = load('SRAS_freq.txt');
x = D(:, 1);
y = D(:, 2);
xData = [min(x(:)), max(x(:))]
yData = [min(y(:)), max(y(:))]
Frequency = reshape(D(:,3), 200, []);
imshow(Frequency, [], 'XData', xData, 'YData', yData);
axis('on', 'image')
impixelinfo;

[Ratty419]

THANKS @Image Analyst VERY GRATEFUL.

[Ratty419]

I repeated the procedure for an optical image data file . It appears the images frequency/velocity data are inconsistent in the image. How do I remove this data from the image? How can I apply this technique to the velocity data and re-plot the new velocity image? @Image Analyst

[Image Analyst]

WHAT data? Explain what is inconsistent in this data or image:

D = load('SRAS_opt.txt');
x = D(:, 1);
y = D(:, 2);
xData = [min(x(:)), max(x(:))]
yData = [min(y(:)), max(y(:))]
Frequency = reshape(D(:,3), 200, []);
imshow(Frequency, [], 'XData', xData, 'YData', yData);
axis('on', 'image')
impixelinfo;c=fprintf('Done!\n')

[Ratty419]

What I mean is that both images have patched spots form -40 to -5 on along the x-axis..... Is it possible to remove these patches to ensure a uniform image along this stretch? Thanks.

[Richard Smith]

If you bring your code to class and ask for assitance, you wont need to find solutions online.

Remember all code will go through turnitin to check it is your own work!