MATLAB: How to assign a value label to a string

label;MATLABregressionstring

Im trying to assign values to 3 string variables of gender so that:

0=nonbinary

1=female

2=male

This is so that im able to add it as a predictor in a simple regression.

However, im not sure how to do this.

Best Answer

It's not clear what you're trying to do but I think you have a list of stings and you're trying to assign them a numerical value according to their group.

gender = {'f' 'm' 'n' 'f' 'm' 'n'}; 
genderGroup = findgroups(gender);         %matlab 2015b or later

If you'd like to assign specific values,

genderGroup = nan(size(gender));
genderGroup(strcmp(gender, 'f')) = 1; 
genderGroup(strcmp(gender, 'm')) = 2; 
genderGroup(strcmp(gender, 'n')) = 0;

However, if this group variable is used as a category in a regression function, you probably don't have to use numerical categories. You might be able to just convert your strings to categories.

categorical(gender)

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The behavior you are seeing is because MATLAB uses the "+" operator as plus operator, and for characters, that means converting them to their ASCII values, in this case "10" and summing those values.

Strings are an exception to this where "s" + "s" will concatenate the strings.

To concatenate two or more characters, I recommend using the "[ ]" bracket syntax. Each character group separated by either spaces or commas inside the brackets will be concatenated together.

So the code below would return what you would expect.

>> res = [newline, newline]

res =

    '
     '

>> res = [newline newline]

res =

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To implement a string version of the newline function, you could write a file called "stringnewline.m" which contains the following:

function out = stringnewline
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If you add that file to the MATLAB path, you will be able to use a string form of the newline function.

MATLAB: How Do I Determine which Group Variables Correspond to the Results of SplitApply

Consider using the second argument output from findgroups?

[G,ID] = findgroups(A) also returns the unique values for each group in ID. For example, if A is {'b','a','a','b'}, then findgroups returns G as [2 1 1 2] and ID as {'a','b'}. The arguments A and ID are the same data type, but need not be the same size.

[G, ID] = findgroups(Gender)
ID =
  2×1 cell array
    {'Female'}
    {'Male'  }

The group IDs are sequential, so ID{1} will always match the entries for G==1, ID{2} matches G==2, etc. The grouping is usually sorted.

Best Answer

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