How to replace a certain value for another one once in a vector without using the index?

vec = [89.7000 9.1000 68.0000 87.7000 91.7000 9.1000]
rep = 50

I have to replace one of the 9.1000s in vec for rep without using indices.

[Star Strider]

I have to replace one of the 9.1000s in vec for rep without using indices.

That does not seem possible to me. I cannot imagine a way to address the elements of a vector without using some sort of indexing.

Answer 1

[Sebastian]

Use this to replace all elements with the value of 9.1 with rep:

vec(vec == 9.1) = rep
vec =
   89.7000   50.0000   68.0000   87.7000   91.7000   50.0000

Alternatively use this to find the indices of the elements and then replace them:

ind = find(vec == 9.1)
ind =
     2     6
vec(ind) = rep
vec =
     89.7000   50.0000   68.0000   87.7000   91.7000   50.0000

If you only want to replace the first element, use this:

vec(find(vec == 9.1, 1)) = rep

vec =

     89.7000   50.0000   68.0000   87.7000   91.7000    9.1000

[Star Strider]

That is implied indexing, since find returns the index.

[Sebastian]

I know but I think there is no way around find if you want to replace only certain elements and not all of them.