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

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John D'Errico
John D'Errico 2018-11-29
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
diadalina 2018-11-29
it is another way to calculate the max ?

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madhan ravi
madhan ravi 2018-11-29

1 个投票

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

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diadalina
diadalina 2018-11-29
编辑：diadalina 2018-11-29
thank you madhan ravi for your answer but i want with diff, if you can help me , thank you.
Jan
Jan 2018-11-29
@diadalina: Accepting an answer means, that the problem is solved.
The diff command is not useful to find the maximum value.
diadalina
diadalina 2018-11-29
no, it is, when we calculate the sign of the difference between two successive numbers.
madhan ravi
madhan ravi 2018-11-29
编辑：madhan ravi 2018-11-29
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
diadalina 2018-11-30
mr ravi what do you want to say by the monotonicity of the vector can you more explain to me please ?
Jan
Jan 2018-12-3
编辑：Jan 2018-12-3
@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
diadalina 2018-12-4
thank you mr Jan, now it is clear for me.

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