I need to save multiple arrays to a text file in the following format:
n=2 %number of arrays
r=3 %number of rows in the first array
1 2 3 % actual data
4 5 6
7 8 9
r=3 %number of rows in the second array
5 6 7 % actual data
1 2 3
7 8 9
Would you help please
Use fprintf. If your arrays are stored in a cell array so that you can iterate through them.
arrays = cell(N, 1); %A cell array of arrays
f = fopen('output.txt', 'w');
fprintf(f, 'n=%i\n', N);
for i=1:N
rows = size(arrays{i}, 1);
fprintf(f, '\nr=%i\n', rows);
for j=1:rows
fprintf(f, '%g ', arrays{i}(N, :));
fprintf(f, '\n');
end
end
fclose(f);
What have you done so far?
As a general rule, for this sort of thing your friends are the functions fprintf, which prints data to a file, and varargin, which allows you to supply a variable-length argument list to a function. A good signature for a function that handles this sort of task might therefore be
function [output_args] = pretty_save_to_file(fName, varargin)
Here fName is the name of the file you'd like your data saved to and varargin is a placeholder for the names of the matrices you'd like to save. Once you've filled in the gory details of the function, you should be able to call it using something like
pretty_save_to_file('output.txt', A, B, C) % prints matrices A, B, and C to output.txt
In addition, since you're looking to determine the number of rows in each matrix, you'll probably find the following snippet involving the size function useful:
[nrows, ncols] = size(A); % Stores the number of rows and columns of A in nrows, ncols
Finally, the fprintf function allows you to specify the desired formatting of your matrix.
Related
I Have a 8x18 structure with each cel containing a column vector of occurrences of a single event. I want to obtain data from some of these fields concatenated in a single array, without having to loop through it. I can't seem to find a way to vertically concatenate the fields I am interested in in a single array.
As an example I create the following structure with between 1 and 5 occurrences per cell:
s(62).vector(8,18).heading.occurrences=[1;2;3];
for i=1:62
for j=1:8
for k=1:18
y=ceil(rand(1)*5);
s(i).vector(j,k).heading.occurrences=rand(y,1);
end
end
end
Now if want to obtain all occurrences in several cells while keeping i constant at for instant i=1 the following works:
ss=s(1).vector([1 26 45]);
h=[ss.heading];
cell2mat({h.occurrences}')
Now I would want to do the same for s, for instance s([1 2 3]).vector([1 26 45]), how would that work? I have tried xx=s([1 2 3]), yy=xx.vector([1 26 45]) but this however yields the error:
Expected one output from a curly brace or dot indexing expression, but there were 3 results.
Is this also possible with a vector operation?
Here's a vectorized solution that accommodates using index vectors for s and the field vector:
sIndex = [1 2 3]; % Indices for s
vIndex = [1 26 45]; % Indices for 'vector' field
v = reshape(cat(3, s(sIndex).vector), 144, []);
h = [v(vIndex, :).heading];
out = vertcat(h.occurrences);
It uses cat to concatenate all the vector fields into an 8-by-18-by-numel(sIndex) matrix, reshapes that into a 144-by-numel(sIndex) matrix, then indexes the rows specified by vIndex and collects their heading and occurrences fields, using vertcat instead of cell2mat.
It's difficult to vectorize the entire operation, but this should work.
% get vector field and store in cell array
s_new = { s(1:3).vector };
% now extract heading field, this is a cell-of-cells
s_new_heading = cellfun(#(x) { x.heading }', s_new, 'UniformOutput', false);
occurences = {};
for iCell = 1:length(s_new_heading)
% use current cell
cellHere = s_new_heading{iCell};
% retain indices of interest, these could be different for each cell
cellHere = cellHere([ 1 26 45 ]);
% extract occurrences
h = cellfun(#(x) x.occurrences, cellHere, 'UniformOutput', false);
h_mat = cell2mat(h);
% save them in cell array
occurences = cat(1, occurences, h_mat);
end
I have a huge text file in the following format:
1 2
1 3
1 10
1 11
1 20
1 376
1 665255
2 4
2 126
2 134
2 242
2 247
First column is the x coordinate while second column is the y coordinate.
It indicates that if I had to construct a Matrix
M = zeros(N, N);
M(1, 2) = 1;
M(1, 3) = 1;
.
.
M(2, 247) = 1;
This text file is huge and can't be brought to main memory at once. I must read it line by line. And save it in a sparse matrix.
So I need the following function:
function mat = generate( path )
fid = fopen(path);
tline = fgetl(fid);
% initialize an empty sparse matrix. (I know I assigned Mat(1, 1) = 1)
mat = sparse(1);
while ischar(tline)
tline = fgetl(fid);
if ischar(tline)
C = strsplit(tline);
end
mat(C{1}, C{2}) = 1;
end
fclose(fid);
end
But unfortunately besides the first row it just puts trash in my sparse mat.
Demo:
1 7
1 9
2 4
2 9
If I print the sparse mat I get:
(1,1) 1
(50,52) 1
(49,57) 1
(50,57) 1
Any suggestions ?
Fixing what you have...
Your problem is that C is a cell array of characters, not numbers. You need to convert the strings you read from the file into integer values. Instead of strsplit you can use functions like str2num and str2double. Since tline is a space-delimited character array of integers in this case, str2num is the easiest to use to compute C:
C = str2num(tline);
Then you just index C like an array instead of a cell array:
mat(C(1), C(2)) = 1;
Extra tidbit: If you were wondering how your demo code still worked even though C contained characters, it's because MATLAB has a tendency to automatically convert variables to the correct type for certain operations. In this case, the characters were converted to their double ASCII code equivalents: '1' became 49, '2' became 50, etc. Then it used these as indices into mat.
A simpler alternative...
You don't even have to bother with all that mess above, since you can replace your entire function with a much simpler approach using dlmread and sparse like so:
data = dlmread(filePath);
mat = sparse(data(:, 1), data(:, 2), 1);
clear data; % Save yourself some memory if you don't need it any more
I have one big cell with N by 1 dimension. Each row is either a string or a double. A string is a variable name and the sequential doubles are its values until the next string (another variable name). For example:
data = {
var_name1;
val1;
val2;
val3;
val4;
val5;
var_name2;
val1;
val2;
var_name3;
val1;
val2;
val3;
val4;
val5;
val6;
val7}
and so on. I want to separate the data cell into three cells; {var_name and it's 5 values}, {var_name and it's 2 values}, {var_name and it's 7 values}. I try not to loop as much as possible and have found that vectorization along with cellfun works really well. Is it possible? The data cell has close to million rows.
I believe the following should do what you're after. The main pieces are to use cumsum to work out which name each row corresponds to, and then accumarray to build up lists per name.
% Make some data
data = {'a'; 1; 2; 3;
'b'; 4; 5;
'c'; 6; 7; 8; 9;
'd';
'e'; 10; 11; 12};
% Which elements are the names?
isName = cellfun(#ischar, data);
% Use CUMSUM to work out for each row, which name it corresponds to
whichName = cumsum(isName);
% Pick out only the values from 'data', and filter 'whichName'
% for just the values
justVals = data(~isName);
whichName = whichName(~isName);
% Use ACCUMARRAY to build up lists per name. Note that the function
% used by ACCUMARRAY must return something scalar from a column of
% values, so we return a scalar cell containing a row-vector
% of those values
listPerName = accumarray(whichName, cell2mat(justVals), [], #(x) {x.'});
% All that remains is to prepend the name to each cell. This ends
% up with each row of output being a cell like {'a', [1 2 3]}.
% It's simple to make the output be {'a', 1, 2, 3} by adding
% a call to NUM2CELL on 'v' in the anonymous function.
nameAndVals = cellfun(#(n, v) [{n}, v], data(isName), listPerName, ...
'UniformOutput', false);
cellfun is for applying a function to each element of a cell.
When you pass multiple arguments to cellfun like that, it takes the ith argument of data, indx_first, and indx_last, and uses each of them in the anonymous function. Substituting those variables in, your function evaluates to x(y : z), for each element x in data. In other words, you're doing data{i}(y : z), i.e., indexing the actual elements of the cell array, rather than indexing the cell array itself. I don't think that's what you want. Really you want data{y : z}, for each (y, z) pair given by corresponding elements in indx_first and indx_last, right?
If that's indeed the case, I don't see a vectorized way to solve your problem, because each of the "variables" has different size. But you do know how many variables you have, which is the size of indx_first. So I'd pre-allocate and then loop, like so:
>> vars = cell(length(indx_first), 2);
>> for i = 1:length(vars)
vars{i, 1} = data{indx_first(i) - 1}; % store variable name in first column
vars{i, 2} = [data{indx_first(i) : indx_last(i)}]; % store data in last column
end
At the end of this, you'll have a cell array with 2 columns. The first column in each row is the name of the variable. The second is the actual data. I.e.
{'var_name1', [val1 val2 val3 val4 val5];
'var_name2', [val1 val2];
.
.
.
Another question on fprintf
I have a matrix s(n,5) that I want to shorten (just take columns 3,4 and 5) into s1(n,3) and save with a different name.
s1=s(:,3:5);
txtfilename = [Filename '-1.txt'];
% Open a file for writing
fid = fopen(txtfilename, 'w');
% print values in column order
% two values appear on each row of the file
fprintf(fid, '%f %f %f\n', s1);
fclose(fid);
I don't think I understood the way to use fprintf and rewrite my new matrix, because it is sorting the values.
Thanks for your help
The problem is that MATLAB stores data in column-major order, meaning that when you do s1(:), the first three values are the first three values in the first column not the first row. (This is how fprintf will read values out of s1.) For example:
>> M = magic(3)
M =
8 1 6
3 5 7
4 9 2
>> M(:)
ans =
8
3
4
1
5
9
6
7
2
You can simply transpose the matrix to output the way you want:
fprintf(fid, '%f %f %f\n', s1.');
Dear stackoverflowers,
I'd like to create a .txt file using matlab.
The content should be separated with tabs.
It should have 3 columns, and the 3rd column should be filled with strings from a cell array.
Let's say
A=[2; 3; 3;];
B=2*A;
C=cell(3,1);
C{1,1}='string1'; C{2,1}='string2'; C{3,1}='string3';
In the end, it should look like this:
2 4 string1
3 6 string2
3 6 string3
I already found out, how to put the 2 matrices in a text file:
dlmwrite('filename.txt', [A B], 'delimiter', '\t')
But how to append the content of the cell?
It would be best, to have only the strings in the file, not the single quotes.
I neither found a solution to this elsewhere, nor did I ask this somewhere else.
I apprechiate all kinds of suggestions.
Try the following:
% Open a file for writing (if you want to append to file use 'a' instead of 'w')
fid = fopen(file,'w');
for i = 1:size(A,1)
fprintf(fid,'%d %d %s\n',A(i),B(i),C{i})
end
fclose(fid)
Hope this helps
the documentation on dlmwrite states:
Remarks
The resulting file is readable by spreadsheet programs.
The dlmwrite function does not accept cell arrays for the input matrix
M. To export a cell array that contains only numeric data, use
cell2mat to convert the cell array to a numeric matrix before calling csvwrite.
To export cell arrays with mixed alphabetic and numeric
data, where each cell contains a single element, you can create an
Excel spreadsheet (if your system has Excel installed) using xlswrite.
For all other cases, you must use low-level export functions to write
your data.
So either you write it as an Excel spreadsheet, or use have to write your own conversion function.
For example
A=[2; 3; 3;];
B=2*A;
C=cell(3,1);
C{1,1}='string1'; C{2,1}='string2'; C{3,1}='string3';
% First solution
f = fopen('filename.txt', 'w');
for n = 1:3
fprintf(f, '%d\t%d\t%s\n', A(n), B(n), C{n});
end
fclose(f);
% Another solution
% create the table as a single cell array with only strings
C2 = [arrayfun(#num2str, [A, B], 'UniformOutput', false) C]'; % <- note the transpose
f = fopen('filename.txt', 'w');
fprintf(f, '%s\t%s\t%s\n', C2{:}); % <- every three entries are written as a line
fclose(f);