Assign NaN to specific rows(based on criteria) for multiple table variables

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Marcel345614
Marcel345614 on 1 Feb 2022
Commented: Marcel345614 on 2 Feb 2022
I want to assign NaN to (time-)table rows that match a criteria (T.Var1~=1). I would like to do this for specific variables in the table.
But instead of doing
T.Var2(T.Var1~=1)=NaN; % Note: My variables are not called Var1, Var2, ... but I simplified it here to these names ;-)
T.Var5(T.Var1~=1)=NaN;
%...
T.Var10(T.Var1~=1)=NaN;
%...
I would like to do this in a shorter code. Is this possible?
I look for something like this:
T.{'Var2','Var5', 'Var7', 'Var10'}(T.Var1~=1)=NaN;

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Accepted Answer

Turlough Hughes
Turlough Hughes on 1 Feb 2022
Ran in:
You can do that as follows:
% Firstly some sample data
T = array2timetable(randi(3,10,5),'Rowtimes',datetime() + seconds(0:9))
T = 10×5 timetable
Time Var1 Var2 Var3 Var4 Var5 ____________________ ____ ____ ____ ____ ____ 01-Feb-2022 16:14:43 2 2 1 1 1 01-Feb-2022 16:14:44 2 1 2 3 3 01-Feb-2022 16:14:45 3 2 2 2 3 01-Feb-2022 16:14:46 1 3 1 3 2 01-Feb-2022 16:14:47 1 3 2 2 3 01-Feb-2022 16:14:48 1 3 3 3 2 01-Feb-2022 16:14:49 3 3 1 1 1 01-Feb-2022 16:14:50 1 3 3 1 3 01-Feb-2022 16:14:51 2 2 1 1 3 01-Feb-2022 16:14:52 1 1 1 3 2
% You can do it using column numbers
T{T.Var1==1,[2 4]} = nan
T = 10×5 timetable
Time Var1 Var2 Var3 Var4 Var5 ____________________ ____ ____ ____ ____ ____ 01-Feb-2022 16:14:43 2 2 1 1 1 01-Feb-2022 16:14:44 2 1 2 3 3 01-Feb-2022 16:14:45 3 2 2 2 3 01-Feb-2022 16:14:46 1 NaN 1 NaN 2 01-Feb-2022 16:14:47 1 NaN 2 NaN 3 01-Feb-2022 16:14:48 1 NaN 3 NaN 2 01-Feb-2022 16:14:49 3 3 1 1 1 01-Feb-2022 16:14:50 1 NaN 3 NaN 3 01-Feb-2022 16:14:51 2 2 1 1 3 01-Feb-2022 16:14:52 1 NaN 1 NaN 2
% or using variable names
T{T.Var1==1,["Var3", "Var5"]} = nan
T = 10×5 timetable
Time Var1 Var2 Var3 Var4 Var5 ____________________ ____ ____ ____ ____ ____ 01-Feb-2022 16:14:43 2 2 1 1 1 01-Feb-2022 16:14:44 2 1 2 3 3 01-Feb-2022 16:14:45 3 2 2 2 3 01-Feb-2022 16:14:46 1 NaN NaN NaN NaN 01-Feb-2022 16:14:47 1 NaN NaN NaN NaN 01-Feb-2022 16:14:48 1 NaN NaN NaN NaN 01-Feb-2022 16:14:49 3 3 1 1 1 01-Feb-2022 16:14:50 1 NaN NaN NaN NaN 01-Feb-2022 16:14:51 2 2 1 1 3 01-Feb-2022 16:14:52 1 NaN NaN NaN NaN
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Turlough Hughes
Turlough Hughes on 1 Feb 2022
Ran in:
No problem. The single quotes are type char and the double quotes are type string. You can see why Var1Var3Var5 came up just by typing it into the command window:
idx = ['Var1' 'Var3' 'Var5']
idx = 'Var1Var3Var5'
whereas when you concatenate strings the result is different:
idx = ["Var1" "Var3" "Var5"]
idx = 1×3 string array
"Var1" "Var3" "Var5"
You could also use a cell array of char's to index by the variable names:
T = array2timetable(randi(3,10,5),'Rowtimes',datetime() + seconds(0:9));
T{T.Var1==1,{'Var3', 'Var5'}} = nan
T = 10×5 timetable
Time Var1 Var2 Var3 Var4 Var5 ____________________ ____ ____ ____ ____ ____ 01-Feb-2022 17:00:03 2 1 3 3 3 01-Feb-2022 17:00:04 2 3 1 2 1 01-Feb-2022 17:00:05 1 1 NaN 3 NaN 01-Feb-2022 17:00:06 3 1 3 2 2 01-Feb-2022 17:00:07 2 3 1 2 3 01-Feb-2022 17:00:08 2 1 1 2 1 01-Feb-2022 17:00:09 1 1 NaN 1 NaN 01-Feb-2022 17:00:10 1 3 NaN 3 NaN 01-Feb-2022 17:00:11 1 2 NaN 3 NaN 01-Feb-2022 17:00:12 1 1 NaN 1 NaN

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More Answers (1)

Benjamin Thompson
Benjamin Thompson on 1 Feb 2022
If you are assigning from a scalar it seems you must do this column by column. Use an index vector to select which rows to assign:
T.Var1 = [1 2 3 4 1]'
T.Var2 = 2*ones(5,1)
T.Var3 = 5*ones(5,1)
T.Var4 = 10*ones(5,1)
I = T.Var1 ~= 1
T2.Var2(I) = NaN
T2.Var3(I) = NaN
T2.Var4(I) = NaN
See the MATLAB help article "Access Data in Tables" for more data reading and writing examples.

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