how to convert .txt file data to a matrix form

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Kamal Bera 2015-3-30

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评论： Kamal Bera 2015-4-22

采纳的回答： Stephen23

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I have a text file 'MatK.txt'(extracted from ANSYS as stiffness matrix) which has data as follows:

MATK: 
[1,1]: 2.250e+007 [1,3]:-1.688e+007 [1,4]: 1.125e+007 
[2,2]: 1.500e+009 [2,5]:-7.500e+008 
[3,3]: 3.375e+007 [3,6]: 1.688e+007 
[4,4]: 4.500e+007 [4,6]: 1.125e+007 
[5,5]: 7.500e+008 
[6,6]: 2.250e+007

in which the value inside [ , ] represents row and column number. since it is a symmetric matrix it only shows the upper triangular part. I want the full 6x6 matrix.

Kindly help me out. Thanks in advance

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Stephen23 2015-3-30

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编辑：Stephen23 2015-4-1

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It is not clear exactly what your question is: are you having difficulty reading this data from the file, or converting the text data into a matrix, or filling the matrix from the upper triangle data given? Below is some code that should cover most of these topics. First we define the given data as a string (is this how you read it from the file?):

>> str = 'MATK: [1,1]: 2.250e+007 [1,3]:-1.688e+007 [1,4]: 1.125e+007 [2,2]: 1.500e+009 [2,5]:-7.500e+008 [3,3]: 3.375e+007 [3,6]: 1.688e+007 [4,4]: 4.500e+007 [4,6]: 1.125e+007 [5,5]: 7.500e+008 [6,6]: 2.250e+007';

Now we can extract all of the numeric data using regexp: Edited to parse the negative values:

>> tok = regexp(str,'\[(\d),(\d)\]: ?(\S+)','tokens');
>> mat = cellfun(@(s)sscanf(s,'%f'),vertcat(tok{:}));

and then place the data in the given locations to get the upper-triangular matrix using sub2ind:

>> out = zeros(max(mat(:,1)),max(mat(:,2)));
>> ind = sub2ind(size(out),mat(:,1),mat(:,2));
>> out(ind) = mat(:,3)
out =
1.0e+009 *
  0.0225         0   -0.0169    0.0113         0         0
       0    1.5000         0         0   -0.7500         0
       0         0    0.0338         0         0    0.0169
       0         0         0    0.0450         0    0.0113
       0         0         0         0    0.7500         0
       0         0         0         0         0    0.0225

From which we can very easily generate the whole matrix using triu:

>> out = triu(out) + triu(out,1).'
out =
1.0e+009 *
  0.0225         0   -0.0169    0.0113         0         0
       0    1.5000         0         0   -0.7500         0
 -0.0169         0    0.0338         0         0    0.0169
  0.0113         0         0    0.0450         0    0.0113
       0   -0.7500         0         0    0.7500         0
       0         0    0.0169    0.0113         0    0.0225

Alternative using textscan:

>> tok = cell2mat(textscan(str(6:end),'[%f,%f]:%f'))

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Kamal Bera 2015-4-1

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STIFFNESS MATRIX .txt

Now it is working. I have another question.If a text file (attached)in which corresponding to each row all the column values are given e.g.

ROW 1 NODE 1 DEG. OF. FR. = ROTZ

0.13513535E+09    2 0.00000000E+00    3 0.91507762E+08    4-0.59130175E+08
0.00000000E+00    6 0.00000000E+00    7 0.00000000E+00    8-0.36603105E+09
0.00000000E+00   10 0.00000000E+00   11 0.00000000E+00   12 0.10701035E+09
0.00000000E+00   14 0.00000000E+00   15 0.00000000E+00   16 0.00000000E+00
0.00000000E+00   18 0.00000000E+00
   ROW   2   NODE     2     DEG. OF. FR. =  UX  
0.00000000E+00    2 0.35000101E+10    3 0.00000000E+00    4 0.00000000E+00
0.25000125E+09    6 0.00000000E+00    7-0.20000063E+10    8-0.33333439E+06
0.00000000E+00   10 0.00000000E+00   11 0.00000000E+00   12 0.00000000E+00
   13-0.20000063E+10   14 0.33333439E+06   15 0.00000000E+00   16 0.00000000E+00
0.00000000E+00   18 0.00000000E+00

and so on upto 18 rows ( Please see the attached file for clarity ). What modification I need to do in my code to get a 18x18 matrix.

Again thank you for your quick responses. It will help me to progress further in my work.

Kamal Bera 2015-4-15

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Hi Mr. Stephen Cobeldick, I am trying to apply your code (see below )to get a matrix of size 1710x1710 from a txt file (attached) as I did earlier to get 6x6 and 18x18 matrices from txt files. Unfortunately it is not working and shows error as

 Subscripted assignment dimension mismatch.
    Error in KSUBmatrix (line 9)
        out(k,:) = val{k}(:,2);

Kindly help me so that I can apply the code for any matrix dimension I wish to extract.It is urgently required.

str = fileread('STIFFNESS MATRIX .txt');        % txt file name STIFFNESS MATRIX extracted from ANSYS
[tok,idx] = regexp(str,'ROW\s+(\d+)\s+NODE\s+(\d+)\s+[^\n=]+=\s+(\w+)','tokens','end');
tok = vertcat(tok{:});
idx = [1+idx,numel(str)];
fun = @(b,e)reshape(sscanf(str(b:e),'%f'),2,[]).';
val = arrayfun(fun,idx(1:end-1),idx(2:end),'UniformOutput',false);
out = zeros(numel(val));
for k = 1:numel(val)
    out(k,:) = val{k}(:,2);
end
K=out;               % required structural stiffness matrix

The file attached is in zip form as it is of large size. If you required the file corresponding to 6x6 or 18x18 matrix cases(for which the given code works nicely), I will attach those separately.

I am egerly waiting for your quick response.

thank you.