MATLAB: Plotting two columns from matrix.

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I am trying to plot Column 4 against Column 10 as a line plot, but only when Columns 8 and 9 are between 0 +/- 0.0005. (Columns 8, 9, 10 are x, y, and z locations).
I would have done this with two if loops which would print the row if the conditions were met. This could have then been plotted. I feel as there are over 400,000 entries this is inefficient (file attached represents a smaller quantity due to size constraints). Prealloaction is not possible as I don't know the size of the final array. What would the best way to go about this?

Best Answer

See Indexing with Logical Values half way down the page
A starter
%%


M = dlmread('matrix.txt');
%%
is_show = abs(M(:,8))<5e-4 & abs(M(:,9))<5e-4;
%%
figure
plot( M(is_show,10), M(is_show,4), '.' )
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