Converting cell to array data with specific string
2 Ansichten (letzte 30 Tage)
Ältere Kommentare anzeigen
Publius
am 16 Nov. 2022
Kommentiert: Steven Lord
am 17 Nov. 2022
Hi,
I am trying to convert data read from a file to a numeric array. The format that it comes in as from an importdata command is:
{'[2, 11, 5, 0] ' }
{'[1, 10, 6, 0] ' }
{'[9, 3, 6, 0] ' }
{'[8, 1, 4, 0] ' }
{'[2, 4, 7, 0] ' }
{'[1, 3, 6, 0] ' }
{'[2, 3, 5, 0] ' }
{'[1, 2, 4, 0] ' }
{'[1, 2, 3, 0] ' }
I want to convert this to a double array of size n by 4. I want to do so without loops, preferably in one line (combined with the importdata command) to keep my code relatively concise. I have tried string, but that spits out an odd answer.
The data file includes those brackets, so I guess if anyone knows how to exclude MATLAB reading those, readmatrix can work (right now, the first and last columns are NaN because of those if I use that command).
Thank you!
2 Kommentare
Cris LaPierre
am 16 Nov. 2022
Please attach your file (or a representative example) to your post using the paperclip icon.
Akzeptierte Antwort
Stephen23
am 17 Nov. 2022
The simplest approach:
M = readmatrix('test.txt', 'TrimNonNumeric',true)
0 Kommentare
Weitere Antworten (2)
Cris LaPierre
am 16 Nov. 2022
Bearbeitet: Cris LaPierre
am 16 Nov. 2022
There are many ways to do this. Here are two. The result of the 2nd option is a table. See this page on Accessing Data in Tables
file = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/1195758/test.txt';
data1 = readmatrix(file,'delimiter',["[","]",","," "],'ConsecutiveDelimitersRule','join',...
'LeadingDelimitersRule','ignore')
data2 = readtable(file,'format','%*c %f %f %f %f %*c')
3 Kommentare
Jan
am 16 Nov. 2022
Bearbeitet: Jan
am 16 Nov. 2022
data = {'[2, 11, 5, 0] '; '[1, 10, 6, 0] '; '[9, 3, 6, 0] '};
value = str2num(sprintf('%s;', data{:}))
Internally str2num is based on eval. Maybe this is mor secure:
data2 = erase(string(data), "[");
data2 = replace(data2, "]" | ",", " ");
s = strjoin(data2);
value = reshape(sscanf(s, '%g'), 4, []).'
1 Kommentar
Steven Lord
am 17 Nov. 2022
If you're using release R2022a or later you can specify Evaluation='restricted' to limit what expressions in the text to be converted are executed.
str2num('[1, 2; 3, 4; 5:6]', Evaluation='restricted')
To preemptively answer your next question no, I don't have a definitive list of what counts as "basic math expressions" for purposes of restricted evaluation. I suspect if you stick to the operators in the Arithmetic Operators, Relational Operators, and Logical Operators sections on this documentation page along with array creation characters like square brackets, comma, semicolon, and colon you're probably okay.
Siehe auch
Kategorien
Mehr zu Structures finden Sie in Help Center und File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!