MATLAB: How to read information from a .txt file and convert it into a matrix

text filetextscanvectorization

Hello, I need to read information from a text file and convert that information into a matrix or a set of vector columns which i can later use.

The information contained in that text file is always in this format ("name_of_something – 45.00 30.45" – basically a name followed by a dash and by two numbers with two decimal algorithms with a space between all of them). The text file i am using goes bellow.

I need to convert that information into a matrix with three columns, one with the name, one with the first numerical value and the last one with the other numerical value.

I dont know how i can do this. I have managed to get it into a cell array by line but that's not quite what i wanted…

Was really hoping you could help me.

Thanks a lot in advance!

Best Answer

S = fileread('frotatego');
info_struct = regexp(S, '^(?<name>.*?)\s+(?<val1>\d+\.\d\d)\s+(?<val2>\d+\.\d\d)\s*$', 'names', 'dotexceptnewline', 'lineanchors');
names = {info_struct.name};
val1 = str2double({info_struct.val1});
val2 = str2double({info_struct.val2});
T = table(names, val1, val2);

(Not tested as my system is busy at the moment)

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MATLAB: Import too large csv data file with strings

No matter what, you're bound by the reading speed of matlab. Probably the fastest way to read the file is to rea it all once with fileread. You can then split the lines with strsplit. It is then a choice of applying either of textscan, strsplit or regexp on each line. You would have to see which is faster.

Here is how I would do it using regexp:

filecontent = fileread('etch.csv');
filelines = strsplit(filecontent, {'\r', '\n'}); %split at line ending. Copes with linux and windows termination
fields = regexp(filelines, '^([^;]*);([^;]*);([^;]*);([^;]*);([^;]*);([^;]*);([^;]*);', 'tokens', 'once'); %only keep the first seven fields
fields = vertcat(fields{:})

The above takes about 3 seconds on my machine to read 85000 rows (only 8 MB of text though).

One thing it hasn't done is parse the date. This is fairly trivial to do with datetime if needed and takes no time at all.

MATLAB: How to convert a single char array in a table with 3 columns

Suppose you have the character vector stored in the variable S. Then:

info_struct = regexp(S, '(?<Year>\d{4})\s+(?<Month>[A-Za-z]{3})\s+(?<Hh>\d+(\.\d+)?)','names');
Year = str2double({info_struct.Year}.');
Month = vertcat(info_struct.Month);
Hh = str2double({info_struct.Hh}.');
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Best Answer

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