Index a percentage of a Matrix

I'm trying to extract the first 85% of one matrix and the last 15% of another to enable me to plot the combustion of non regular shaped solid fuels but haven't been able to so far.

Answer 1

[dpb]

85% of what--the indices, the values, ...? And, if it's is a matrix, what about shape? Matter where they came from or just overall, or...????

Anyway,

1. %age of number of elements in matrix --> x(1:round(0.85*numel(x)))
2. elements within %age of max in matrix--> x(x<=0.85*max(x(:)))

Other logical direction readily extensible from above.

[dpb]

[OP Answer moved to Comment -- dpb]

Sorry they are single line matrices. Lengths will change depending of the fidelity that I require.

[dpb]

" depending of the fidelity that I require."

What does that mean? Still don't say what it is that you mean by percentage. Give an example (minimally sized) input and an expected output and the rule(z) by which you decide that's the right answer...otherwise, what's wrong with the above?