MATLAB - Need to make a cell array from a text column file

Question

I have a database from UCI Machine Learning (Abalone Database)and I need to separate the first column, which is a character, from the other columns, which are double.

The second part I already have with this code:

abaloneData = csvread('abalone.data',0,1);

I tried a lot to gatter the first part to use on KNN, but I failed every time.

Thanks.

EDIT1:

read_data.m

function [features, labels] = read_data()
    features = csvread('abalone.data',0,1);

    fileID = fopen('abalone.data');
    data = textscan(fileID,'%s %*[^\n]', 'Delimiter',',');
    fclose(fileID);
    labels = cell2mat(data{1});
end

knn.m

[features,labels] = read_data();

Mdl = fitcknn(features,labels);

This is done with textscan

marsei
– marsei

2015-05-10 21:01:14 +00:00
Commented May 10, 2015 at 21:01 — marsei
– marsei, Commented May 10, 2015 at 21:01

Ryan J. Smith · Accepted Answer · 2015-05-10 21:05:53Z

1

The problem, as you've probably realized by now, is that csvread() only works for numeric values. Instead you need to use textscan() to deal with strings / characters. Try this:

fileID = fopen('abalone.data');
data = textscan(fileID,'%s %*[^\n]', 'Delimiter',',');
fclose(fileID);
labels = cell2mat(data{1});

This will open the file and read in the first column as a string, skipping the remaining elements in each row. Finally, this data gets converted from cell to a char vector called labels

answered May 10, 2015 at 21:05

Ryan J. Smith

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8 Comments

Minoru Over a year ago

Your code gives me an array of char, but when I try to use the KNN, I get this error: ??? Undefined function or method 'fitcknn' for input arguments of type 'double'.. Do you know what's the problem? I'll edit the question to add the entire code.

Ryan J. Smith Over a year ago

Your edited code works fine for me. fitcknn() is a function belonging to the statistics toolbox. Are you sure you have access to this toolbox?

Minoru Over a year ago

I am. If you want, I can print the help response.

Ryan J. Smith Over a year ago

In your matlab command line, execute ver. Double check that you see Statistics Toolbox in the list that is returned. You can check further with help fitcknn to ensure you have access to that function.

Minoru Over a year ago

Downloaded the last version of Matlab and it worked great! Thanks, @Ryan!

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il_raffa · Accepted Answer · 2015-05-10 21:03:37Z

0

You can try using textscan if the number of columns is the same for each row:

fp=fopen('f.txt','rt')
a=textscan(fp,'%c%f%f%f%f%f%f%f%f','delimiter',',')
fclose(fp)

the cellarray contains the data stored in the file.

Its size should be (1xn) where "n" is the number of columns of the file.

answered May 10, 2015 at 21:03

il_raffa

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1 Comment

Minoru Over a year ago

This one returns an array with all the text elements. I need only the first column.

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