How to remove Y value for given X

I have two columns, X and Y.

The X column is a series of consecutive numbers (1,2,3...). The Y column is my data.

I want to make Y=NaN at certain X values

for example, lets say: x= 1,2,3,4,5 and y= .4,.6,.2,.6,.9

I want to remove the y=.6 that corresponds to x=4 How do I do this?

Thanks!

Answer 1

[David Fletcher]

data=[1 0.4;2,0.6;3,0.2;4,0.6;5 0.9]
index=data(:,1)==4;
data(index,2)=NaN

Something like this?

[Devon Fisher-Chavez]

Yes, except my actual X and Y columns are extremely large and I dont want to combine them into one line.

I was hoping I could do something like "if X=... then Y= NaN" except in Matlab language

for a single value (ex. 4) I was able to say

y(x == 4) = NaN

But I can only do it for a single value of X. I'm a total novice haha

[David Fletcher]

If you want to do it for multiple x values you could chain the clause together with logical or

y(x == 4|x==5|x==7) = NaN

it could become a bit cumbersome if you want to screen out a lot of x values though, so you could index with a vector of the scalers you want to screen out

y(any(x==[1 2 5 6 9])')=NaN

[Devon Fisher-Chavez]

I tried "y(any(x==[1 2 5 6 9])')=NaN" but it says "matrix dimensions must agree"

[David Fletcher]

Sorry, it's probably because I was working with a row vector rather than a column - transpose it [1 2 5 6 9]'

y(any(x==[1 2 3]')')=NaN

[Devon Fisher-Chavez]

That works! thank you so much!

[David Fletcher]

OK no probs