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How to find the index of string column in a table?

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How to get the column ids of a table with string column.
LastName = {'Sanchez';'Johnson';'Li';'Diaz';'Brown'};
Age = [38;43;38;40;49];
Health = {'Fair';'Poor';'Excellent';'Good';'Fair'};
Height = [71;69;64;67;64];
Weight = [176;163;131;133;119];
BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];
T1 = table(LastName,Age,Health,Height,Weight,BloodPressure)
In the above example the first and third columns are of string datatype.
So I wanted to get
idx = [1 3];
How do I find the index of string column?

Accepted Answer

Cris LaPierre
Cris LaPierre on 25 Apr 2023
First comment - none of your table variables are strings. They are cell arrays of character vectors. That may matter depending how you implement a solution.
There are a couple ways depending on what you ultimately want to do. If you want to extract the colums, see the Access Data in Tables doc page. Use this syntax: S = vartype(type); T{rows,S}
LastName = {'Sanchez';'Johnson';'Li';'Diaz';'Brown'};
Age = [38;43;38;40;49];
Health = {'Fair';'Poor';'Excellent';'Good';'Fair'};
Height = [71;69;64;67;64];
Weight = [176;163;131;133;119];
BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];
T1 = table(LastName,Age,Health,Height,Weight,BloodPressure)
T1 = 5×6 table
LastName Age Health Height Weight BloodPressure ___________ ___ _____________ ______ ______ _____________ {'Sanchez'} 38 {'Fair' } 71 176 124 93 {'Johnson'} 43 {'Poor' } 69 163 109 77 {'Li' } 38 {'Excellent'} 64 131 125 83 {'Diaz' } 40 {'Good' } 67 133 117 75 {'Brown' } 49 {'Fair' } 64 119 122 80
S = vartype("cell");
T1(:,S)
ans = 5×2 table
LastName Health ___________ _____________ {'Sanchez'} {'Fair' } {'Johnson'} {'Poor' } {'Li' } {'Excellent'} {'Diaz' } {'Good' } {'Brown' } {'Fair' }
However, if you do want the index number, the most direct way I can think of is to use varfun with iscell.
idx_LI = varfun(@iscell,T1,'OutputFormat','uniform')
idx_LI = 1×6 logical array
1 0 1 0 0 0
C = 1:width(T1);
idx = C(idx_LI)
idx = 1×2
1 3

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