How do I replace an element from a cell array?

Question

I have a cell array:

A = {NaN, ‘k’, ‘m’, ‘n’}

I want to replace all but the 3rd element of A with NaNs to obtain

B = {NaN, NaN, ‘m’, NaN}

Please, any help/suggestions on how I could go about this? Also, is it possible to do this with a single line of code?

Can you be a bit more specific? how general should the solution be? Do you have an array of integers that contain the indices of the elements that should be replaced with NaNs or how do you know which elements should be replaced? — Julian
– Julian, Commented Feb 9, 2017 at 14:12
Why are you using double NaN's in combination with characters? weird combination to me — JHBonarius
– JHBonarius, Commented Feb 9, 2017 at 14:17
Good question @julian59189. I actually couldn't think of a better way to state the problem as the main code is a bit cumbersome and might take some pain to understand - hence i decided to make the question simple and hope that i would get an answer that i could adapt. For the last part of your question, a couple of 'IF' statements are to decide the particular element to be replaced. Not to worry though, Suever's 2nd solution is ideal for me. Thanks! — User110
– User110, Commented Feb 9, 2017 at 14:38
@J.H.Bonarius, weird combination indeed, but it does serve the purpose. — User110
– User110, Commented Feb 9, 2017 at 14:47

Suever · Accepted Answer · 2017-02-09 14:24:24Z

1

You could create a new array of all NaN's and then replace the third element with the value from the initial cell array

B = num2cell(nan(size(A));
B(3) = A(3);

Alternately, you can overwrite the other values with:

B = A;
B([1 2 4]) = {NaN};

As far as a single line of code, the number of lines is quite irrelevant. What's important is readability and performance. These two things are not necessarily correlated with the number of lines.

edited Feb 9, 2017 at 14:24

answered Feb 9, 2017 at 14:14

Suever

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3 Comments

Sardar Usama Over a year ago

deal is not necessary. I think B([1:2 4:end]) = {NaN} is better. No?

Suever Over a year ago

@Sardar_Usama Ah yes. If you rely on comma-separated values on the left it is necessary but the () assignment is a better option. Thanks

User110 Over a year ago

Many thanks @Suever. Works perfectly (the 2nd code suits me more). Actually i have the cell array as a p x 4 matrix in which case i am to perform certain task by looping through the array row-wise. Hence, i had to add the number of rows to your code as: [B{p, [1 2 4]}] = deal(NaN); and i was surprised it still worked.

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