Collapse logical table into cell strings that contains the table's variable names

I have a n x m logical truth table in the format where "a b c d" are the table variable names

exampleTable =

5×4 table

a b c d

_____ _____ _____ _____

false false false false

true true true true

false false true true

true false true false

false false false true

and I would like to collapse it into a cell array of height n like below. Each row n is a cell array of strings that contains the name of the variable (column) when the entry is true

{{''}; {'a','b','c','d'}; { 'c','d'}; { 'a','c'}; {'c'}}

I imagine I can do something with cellfun, but I'm a little stuck. Thanks for your help!

Answer 1

[Walter Roberson]

temp = [    false    false    false    false
    true     true     true     true 
    false    false    true     true 
    true     false    true     false
    false    false    false    true ];
exampleTable = array2table(temp, 'VariableNames', {'a', 'b', 'c', 'd'})

exampleTable = 5×4 table
      a        b        c        d  
    _____    _____    _____    _____

    false    false    false    false
    true     true     true     true 
    false    false    true     true 
    true     false    true     false
    false    false    false    true 

varnames = exampleTable.Properties.VariableNames;
output = rowfun(@(r) varnames(r), exampleTable, 'SeparateInputs', false, 'OutputFormat', 'cell')

output = 5×1 cell array
    {1×0 cell}
    {1×4 cell}
    {1×2 cell}
    {1×2 cell}
    {1×1 cell}

output{2}

ans = 1×4 cell array
    {'a'}    {'b'}    {'c'}    {'d'}

[Michael Shagam]

beautiful, thank you! rowfun is a new one to remember

[Michael Shagam]

@Walter Roberson followup question. In some later existing code, I use ismember() to do a generic query for a condition. I was hoping to be able to do something like shown to return a true when a row contains an 'a' and/or 'c', but I get this error

ismember(output, {'a' 'c'})

Error using cell/ismember (line 34)

Input A of class cell and input B of class cell must be cell arrays of character vectors, unless one is a character vector.

a ugly workaround is this:

cell2mat(cellfun(@(x)any(ismember(x, {'a' 'c'})), output, 'UniformOutput', false))

ans =

5×1 logical array

0

1

1

1

0

but I'd rather keep my simple ismember() query. Is there a way I can modify the class/format of output, or do I need a stronger query?

[Walter Roberson]

If you need to do those kinds of queries, you are better off sticking with the original representation.

mask = exampleTable.a | exampleTable.c

or even

mask = any(exampleTable{:,{'a', 'c'}},2);