MATLAB: Tables: Create new variables by modifying existing ones

cell arraysfilterstringstringstable

Dear All,

I have a table and I would like to create new variables (columns) by modfying existing ones. I have seen examples where poeple apply functions, but these were typically restricted to numerical operations. Supoose I have the following table:

 A     B      C 
obs1  te:st   X
obs2  test    Y

I would like to create

 A     B       C     D 
obs1  te:st    X   testX
obs2  test     Y   testY

So:

Drop special characters (":")
Append two string columns.

Can anyone help me out?

Thanks in advance!

Best Answer

Use regexprep to replace patterns (with empty strings in your case), and strcat to concatenate cell arrays of strings:

t = cell2table({'obs1', 'te:st', 'X'; 'obs2', 'test', 'Y'}, 'VariableNames', {'A', 'B', 'C'})
t.D = strcat(regexprep(t.B, '\W', ''), test.C)

The regular expresion I've used will drop any character other than [a-ZA-Z0-9_]

Related Solutions

MATLAB: How to convert all the cell in a columns from char to string

Hum! it's not actually that easy as you can't use the syntax yourtable(:, somecolumns) to change the type of the column from cell array to string.

Option 1: use . indexing over the char columns

for columnname = yourcharcolumnnames  %where yourcharcolumnnames is a cell array of the char column names
   yourtable.(columnname{1}) = string(yourtable.(columnname{1}));
end

Option 2: create an auxiliary function for varfun that can take any column type

function column = convertcolumn(column)
   if iscell(column) && ~isempty(column) && ischar(column)
      column = string(column);
   end
end

which you use with varfun:

newtable = varfun(@convertcolumn, yourtable);

MATLAB: Tables: Transform Variablenames

It's easy to turn 'x2_28_2019' into a datetime, that's just

>> datetime('x2_28_2019','InputFormat','''x''MM_dd_yyyy')
ans = 
  datetime
   28-Feb-2019

You can do that on t.Properties.VariableNames to convert them all.

The more difficult question is what do you want to do with them next? You can't use datetimes as the variable names of a table, although you can use them as the row times of a timetable -- rotating 90 deg, in effect.

Best Answer

Related Solutions

MATLAB: How to convert all the cell in a columns from char to string

MATLAB: Tables: Transform Variablenames

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