# Convert categorical back to integer

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Steven Niggebrugge on 22 Dec 2019
Answered: Eric Sofen on 10 Jan 2020
Hi,
i convert an integer to a categorical
a=[-1 0 1]
b=categorical(a)
now how do i convert b back to the same integers in a?
Just can't find the function to do this.
thanks,
steven

#### 1 Comment

dpb on 22 Dec 2019
>> str2num(char(b(:)))
ans =
-1
0
1
>>
But, not recommended; the underlying content of a categorical variable aren't really numeric even if they are numbers. The representation internally is an ordered set of the integers 1:N as I'm sure you've already discovered via double()
>> categories(b)
ans =
3×1 cell array
{'-1'}
{'0' }
{'1' }
>>
Gives the values of the categories that make up the unique elements but not the corresponding location in the original array.

Eric Sofen on 10 Jan 2020
Peter's answer to this similar post provides a few other suggestions to consider.

R2019a

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