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

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?

Answer 1

[Cris LaPierre]

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