How to replace string values in a column of a table into numeric?
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Vaishali Ravi
am 3 Aug. 2020
Bearbeitet: Hamidreza
am 21 Sep. 2022
I have a table X
It has a column named 'fruit' with string values such as {'apple','orange','grapes'}, There are 13 different string values in the column 'fruit'
Now I need to change it as if apple or orange then 1, grapes then 2 and so on.
How can I do that?
4 Kommentare
Walter Roberson
am 3 Aug. 2020
you need to replace the entire table variable if you are changing datatype.
It is often easier to add a new variable with the derived data and either leave the old data or delete the variable.
By the way, use ismember and the second output to find the index of the string. Use the index of the string to index into a vector that maps to numeric values, the thus allowing you to map orange and apple to the same number.
This can be done in a small number of vectorized lines m
Akzeptierte Antwort
Walter Roberson
am 3 Aug. 2020
fruit_types = {'apple', 'orange', 'grape', 'banana', 'kumquat', 'peach', 'tomato', 'strawberry', 'pineapple', 'kiwi', 'blueberry', 'durian', 'avacodo'};
fruit_value = [ 1, 1, 2, -4, 5.3, 1 3 5.3, 11, 2, -5.3, 1, 4];
[wasfound, idx] = ismember(X.fruit, fruit_types);
f_values = nan(length(idx), 1));
f_values(wasfound) = fruit_value(idx(wasfound));
X.fruit_value = f_values;
1 Kommentar
Hamidreza
am 21 Sep. 2022
Bearbeitet: Hamidreza
am 21 Sep. 2022
When I run your code I get the error message below:
Error using cell/ismember (line 34)
Input A of class double and input B of class cell must be cell arrays of character vectors, unless one is a character vector.
Any advice to resolve it?
Thanks,
Hamid
Weitere Antworten (1)
Cris LaPierre
am 3 Aug. 2020
X.fruit = categorical(X.fruit);
X.fruit = renamecats(X.fruit,{'apple','orange','grapes'},{'1','2','3'});
4 Kommentare
Cris LaPierre
am 4 Aug. 2020
You have to combine all 3 lines of code:
- Convert to categorical
- Rename categories
- Convert categories to double
% set up a table variable with 20 repeating fruit names
fruit = {'apple','orange','grapes'}';
ind = randi(3,20,1);
fruit = fruit(ind);
X = table(fruit)
Here you see the text values for fruit
X =
20×1 table
fruit
__________
{'apple' }
{'apple' }
{'grapes'}
{'grapes'}
{'orange'}
{'grapes'}
{'grapes'}
{'apple' }
{'orange'}
{'orange'}
{'grapes'}
{'apple' }
{'orange'}
{'orange'}
{'orange'}
{'grapes'}
{'apple' }
{'grapes'}
{'orange'}
{'apple' }
Now convert the text to numbers
% Change names to numbers
X.fruit = categorical(X.fruit);
X.fruit = renamecats(X.fruit,{'apple','orange','grapes'},{'1','2','3'});
X.fruit = str2double(string(X.fruit))
Now you see the fruit values are numbers
X =
20×1 table
fruit
_____
1
1
3
3
2
3
3
1
2
2
3
1
2
2
2
3
1
3
2
1
Use summary to confirm fruit is now a double.
>> summary(X)
Variables:
fruit: 20×1 double
Values:
Min 1
Median 2
Max 3
Siehe auch
Kategorien
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