18 views (last 30 days)

I have one matrix, A, that is a 1x137 that consists of all of maximum index values of another matrix, B, 137x145.

I am plotting B using "imagesc()" by defining a grid to plot it on like so:

imagesc((xGrid2(1,:,1)),permute(yGrid2(1,1,:), [3 1 2]),((B)))

xGrid2(1,:,1) is a 1x145 matrix that spans from -15.4 to 46.01, and permute(yGrid2(1,1,:), [3 1 2]) is a 137x1 matrix that spans from -4.582 to 53.42.

Now, I want to plot the maximum index values of A onto B but am not sure how to do this. I am able to perform this without defining a grid easily however I want to plot A and B on the defined grid above. If I plot them together without using a user defined grid and save the corresponding x and y values of where the index maximum values lie, I have to perform a scaling factor to correct the x and y coordinates to fit my defined grid.

Thus, how can I go about plotting the maximum index values on a defined grid AND THEN extract the corresponding x and y values of these maximums?

I can use "impixelinfo()" to extract the x and y at each point but that would involve hard coding the coordinates of each point, I would like it to be a bit more automated..

Thanks for the help.

Spencer Chen
on 16 Jan 2020

Let's separate your problem into 2 parts: (1) Plotting problem. (2) Finding location of you Maximum on the xGrid2.

I'll start with (2). If you have not used the max() function to extract your maximums, then you read up a little more on it -- it will give you the indices of your maximum value:

[A,IB] = max(B,[],2);

xA = xGrid2(1,IB,1);

I believe xA should give you the coordinates that you want to get.

Now, as for (1) plotting, you can hold the axis and use plot() or scatter():

hold on

plot(xGrid2(1,IB,1), squeeze(yGrid2(1,1,IB)), '.')

hold off

Note the use of the squeeze() function. It should replace your permute() operations.

(Code not tested...)

Blessings,

Spencer

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!
## 1 Comment

## Direct link to this comment

https://au.mathworks.com/matlabcentral/answers/500613-plotting-points-at-specified-index-values#comment_786742

⋮## Direct link to this comment

https://au.mathworks.com/matlabcentral/answers/500613-plotting-points-at-specified-index-values#comment_786742

Sign in to comment.