# get the matrix values under a line

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Armindo2015-10-11
Hi,
I have a matrix of data (120x90) that I plot and then I draw a diagonal line by doing something like:
plot([x1,x2],[Y1,Y2],'g.');
I need to be abe to determine all the matrix values under the line. Any idea about how to perform this efficiently?

### 回答（3 个）

Image Analyst 2015-10-12
If you have the Image Processing Toolbox, you can get this information from the function improfile().
improfile(I,xi,yi,n) returns pixel intensity values, where n specifies the number of points to include.
c = improfile(___) returns the intensity values in c, an n-by-1 vector, if the input is a grayscale intensity image, or an n-by-1-by-3 array if the input is an RGB image.
[cx,cy,c] = improfile(I,xi,yi,n) additionally returns the spatial coordinates of the pixels, cx and cy, of length n.
##### 3 个评论显示隐藏 2更早的评论
Dear Image Analyst,
I want to thank you personally for all your help, suggestions and solutions to Matlab issues and questions. Lately, I am doing much images post-processing of optical obtained images and data. Wherever I stuck and google for a proper solution, I find the best and easiest solution from you.
Thank you again and keep up the good work
Regards form Germany
Rahand

Star Strider 2015-10-11
You would have to define every (x,y) pair along the line, in terms of the row and column values of the matrix coordinates. That will likely be straightforward when you derive an equation for the line.
I am not certain what information you want from the matrix, but you might also consider using the interp2 function if you want to interpolate the values of the matrix.
##### 4 个评论显示隐藏 3更早的评论
Star Strider 2015-10-12
My pleasure.
I tested that code thoroughly so it should be robust. I’ll do my best to help you adapt it if necessary, but I wrote it years ago (and haven’t used it much since), so I’d have to remember what I did.

William Chamberlain 2018-10-17
Bresenham's line algorithm implementations:
##### 1 个评论显示隐藏 无
Image Analyst 2018-10-17
Using improfile() with the 'nearest' option would also do that, if he wanted to go to the nearest pixel instead of doing subpixel interpolation.

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