how can we do this?

i want to calculate the maximum of vectors éléments and its position using the diff command, can any one help me ?

[John D'Errico]

Why not just use max? Since it does exactly what you claim to want.

diff as applied to a vector will not help you here.

[diadalina]

it is another way to calculate the max ?

Answer 1

[madhan ravi]

[value,index]=max(vector) %use max which does exactly what you want

[diadalina]

thank you madhan ravi for your answer but i want with diff, if you can help me , thank you.

[Jan]

@diadalina: Accepting an answer means, that the problem is solved.

The diff command is not useful to find the maximum value.

[diadalina]

no, it is, when we calculate the sign of the difference between two successive numbers.

[madhan ravi]

Anytime :) @diadalina , thank you Jan

But it depends upon the monotonicity of the vector also so like John and Jan suggests it's not useful

[diadalina]

mr ravi what do you want to say by the monotonicity of the vector can you more explain to me please ?

[Jan]

@diadaline: Use these three inputs:

a = rand(1, 10)
b = 1:10
c = 10:-1:1

While using max() is easy here, there is no chance to use diff() to find a maximum value. But here, diff can be useful:

d = sin(0:0.001:pi)

Here you have the additional knowledge, that the elements are monotonically increasing and decreasing. Together with this knowledge diff can be used:

find(diff(d) <= 0, 1, 'first')

max() is more useful, because it works in the general case also.

[diadalina]

thank you mr Jan, now it is clear for me.