logical to index values convert

I have a set of values, like a = [1 2 3 4 5 6 7 6 5 4 3 2 1]; % 1x13 double

Now, i wish to get the index of value for which numbers are increasing and decreasing.

For this i used,

for i = 1:length(a)-1
out = find(a(i)>a(i+1));
in = find(a(i)<a(i+1));
end

however, it gives me error.

so i tried,

for i = 1:length(a)-1
out = (a(i)>a(i+1));
in = (a(i)<a(i+1));
end

Now, I have logical o/p. How to fetch index numbers from this logical o/p?

Answer 1

[Stephan]

Hi,

try:

a = [1 2 3 4 5 6 7 6 5 4 3 2 1]; % 1x13 double
for i = 1:length(a)-1
    out(i) = (a(i)>a(i+1));
    in(i) = (a(i)<a(i+1));
end
in = find(in)
out = find(out)

Note that you can get the same reult without a loop:

in_easy = find(diff(a)>0)
out_easy = find(diff(a)<0)

Best regards

Stephan