How to assign Nans to specific column, not entire row

Question

Tanika Bawa 2022-3-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1669259-how-to-assign-nans-to-specific-column-not-entire-row

评论： Scott MacKenzie 2022-3-11

采纳的回答： Scott MacKenzie

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Hello!

I am trying to assign NaNs to values under 0.95, but only for the rows in column 4, not all of the columns.

Before, I used:

ZB1array = table2array(ZB1);
idx = ZB1array(:,4) < 0.95;
ZB1array(idx,: ) = NaN;

This successfully assigned NaNs, but to the entire row. In order to assign them to rows only in column 4 I tried:

ZB1array(idx, ZB1array(:,4)) = NaN;

But this returns the error 'Index in position 2 is invalid. Array indices must be positive integers or logical values.'

Does anyone know what I should do? Thanks!

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Answer 1

Scott MacKenzie 2022-3-11

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https://ww2.mathworks.cn/matlabcentral/answers/1669259-how-to-assign-nans-to-specific-column-not-entire-row#answer_915169

编辑：Scott MacKenzie 2022-3-11

在 MATLAB Online 中打开

Your first attempt was almost correct. Here's the fix:

ZB1array = rand(5,5) % test data
ZB1array = 5×5
    0.7621    0.6576    0.7379    0.1125    0.0982
    0.5320    0.2791    0.8808    0.4043    0.0584
    0.5336    0.4350    0.4302    0.1737    0.6654
    0.7437    0.6955    0.5260    0.9517    0.3347
    0.8565    0.0006    0.9451    0.0728    0.1189
idx = ZB1array(:,4) < 0.95; 
ZB1array(idx,4) = NaN % must specify column 4
ZB1array = 5×5
    0.7621    0.6576    0.7379       NaN    0.0982
    0.5320    0.2791    0.8808       NaN    0.0584
    0.5336    0.4350    0.4302       NaN    0.6654
    0.7437    0.6955    0.5260    0.9517    0.3347
    0.8565    0.0006    0.9451       NaN    0.1189