Read mixed numbers in Matlab

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John Smith
John Smith el 22 de Dic. de 2018
Comentada: Stephen23 el 30 de Dic. de 2018
Dear Sir/Madam,
I have a data file containing text and mixed number like this: (see the file attached data.txt.)
AA, BB, 28 21/64, 28 45/64,
AA, BB, 1/64, 11/64,
the mixed number have format:
integer space numerator/denominator
I would like to read the data file in matlab as
AA, BB, 28.328125, 28.703125,
AA, BB, 0.015625, 0.171875,
i. e. read mixed numbers and convert them into decimal numbers.
What Matlab command to use? I would greatly appreciate it if you left your code and running output.
I am using MATLAB R2014a.
Thank you

Respuesta aceptada

Stephen23
Stephen23 el 23 de Dic. de 2018
Editada: Stephen23 el 23 de Dic. de 2018
opt = {'CollectOutput',true,'Delimiter',','};
fmt = repmat('%s',1,4);
[fid,msg] = fopen('data.txt','rt');
assert(fid>=3,msg);
C = textscan(fid,fmt,opt{:})
fclose(fid);
C = C{1}; % raw character data in a cell array.
% Convert fractions to numeric:
foo = @(v) sum([v(1:end-2),v(end-1)/v(end)]);
baz = @(s) foo(sscanf(s,'%d%*[ /]'));
M = cellfun(baz,C(:,3:4))
Giving:
M =
28.328125 28.703125
0.031250 0.046875
and the string data is in C. If you want the numeric data reinserted back into C then use num2cell:
>> C(:,3:4) = num2cell(M)
C =
'AA' 'CC' 28.328125 28.703125
'AA' 'CC' 0.031250 0.046875
  14 comentarios
John Smith
John Smith el 30 de Dic. de 2018
Dear Stephen,
I would like to ask you the following question:
I have a data file like this
tmp =
121 12 6914 0.5625
122 -48 6853 0.29688
119 48 6914 0.17188
125 -12 6853 0.078125
125 4 6853 0.4375
119 5 6832 0.20313
119 4 6832 0.039063
119 -4 6832 0.023438
I would like re-group (or reduce) it with following conditions:
For any row, if column 1 AND column 3 of this row is identical with any column 1 AND column 3 of any other row. Then reduce to one new row with new value of column 2, this new value of column 2 is the sum of original values of column 2. Column 1 is kept the same, Column 4 is not important.
So for above data, I expect to have the answer:
119 5 6832 0.20313 % 5+4-4=5
122 -48 6853 0.29688
125 -8 6853 0.4375 % -12+4=-8
121 12 6914 0.5625
119 48 6914 0.17188
Thank you very much
Stephen23
Stephen23 el 30 de Dic. de 2018
@John Smith: that is quite a different topic. Please ask a new question about that.

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Más respuestas (2)

Brian Hart
Brian Hart el 22 de Dic. de 2018
Here's some code to read the data in as a table, then update the mixed number values in each row to the decimal...
T = readtable("C:\Users\MATLAB\Desktop\data.txt",'Delimiter',',','ReadVariableNames',false)
numRows = size(T,1);
for i = 1:numRows
for j=3:4
tmpstr = T{i,j};
tmpstr=tmpstr{:};
tmpstr=strrep(tmpstr, '/',' ');
mixedVal = sscanf(tmpstr,'%d');
if size(mixedVal,1) == 2
decVal = mixedVal(1)/mixedVal(2);
else
decVal = mixedVal(1) + mixedVal(2)/mixedVal(3);
end
T(i,j) = {num2str(decVal)};
end
end
disp(T)
  1 comentario
John Smith
John Smith el 23 de Dic. de 2018
Editada: per isakson el 23 de Dic. de 2018
Thank you Brian,
The code give me those errors: (I am using Matlab R2014a)

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Guillaume
Guillaume el 22 de Dic. de 2018
Editada: Guillaume el 24 de Dic. de 2018
I would recommend that you modify whatever is creating these files so that it creates files that don't have such an unusual format.
As it is, the following should work but is not particularly good code:
data = readtable('data.txt', 'Delimiter', ',', 'ReadVariableNames', false);
data = [data(:, [1 2]), ... %leave text variables unchanged
varfun(@(var) cellfun(@(var) str2num(strrep(var, ' ', '+')), var), data, 'InputVariables', [3 4])]; %convert 'numeric' variables
It simply replaces the space by + and use num2str to parse the expression which is simple but dangerous.
edited to add missing input to cellfun and wrong function use
  3 comentarios
Guillaume
Guillaume el 23 de Dic. de 2018
Editada: Guillaume el 23 de Dic. de 2018
Sorry,forgot the input to cellfun. Fixed now.
In the future, please copy/paste the error as text rather than a screenshot.
Note: the advantage of my answer over the other proposed ones, is that it will parse correctly
28 21/64
21/64
28
Guillaume
Guillaume el 24 de Dic. de 2018
John wrote in a comment now deleted: "Could you please make your code also apply to decimal numbers (as well as mixed number). The reason is that some data has mixed numbers, some data use decimal numbers. I would like have one code fits all. "
As I pointed out, my answer already does that. In a much simpler way. Also note that the numeric columns are stored as vectors which is more memory efficient and easier to use than a cell array of scalars.

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