I need to import some text files as matrix In Matlab. Can anyone help me for code please? Here is the my text file names.
elist_S06n1.txt
elist_S06n2.txt
elist_S06n3.txt
elist_S06n4.txt
elist_S07n1.txt
elist_S07n2.txt
elist_S07n3.txt
elist_S07n4.txt
.
.
.
elist_S27n5.txt
So, till elist_S09n1.tx n is going 1 through 4, then it is going 1 through 5.
Thank you in advance.
Thanks for your update so we can see what you have tried so far.
It seems to me that you have difficulties generating the proper filename. Instead of looping over your cell array index, you could use two loops, one from 6 to 27 and the other from 1 to 4 or 5. Based on these values, you can easily generate the desired filename (mind the leading zero!). Within the loop, you keep track of an index for the resulting cell array.
By the way, if I count the number of files, I arrive at a total of 18*5 + 4*4 = 106 and not 95.
The code:
numfiles = (27-9)*5 + (9-5)*4;
mydata = cell(1, numfiles);
idx = 0; % index for mydata
n = 4;
for k1 = 6:27
if k1 == 10
n = 5; % switch to 5 files if k1 reaches 10
end
for k2 = 1:n
idx = idx+1;
myfilename = sprintf('elist_S%02dn%d.txt', k1, k2);
mydata{idx} = importdata(myfilename);
end
end
Related
I would like to ask if there is a more efficient code to do the following task:
a = cell(10,1);
for i = 1 : 10
a{i,1} = randn(200,5);
end
for j =1:5
b{j} = [a{1,1}(:,j) a{2,1}(:,j) a{3,1}(:,j) a{4,1}(:,j) a{5,1}(:,j)];
end
Thank you!
Your solution works just fine. This is slightly more compact (and easier to generalize). If all cells contain matrices of the same size, you can merge them in one matrix, and pick one column every n:
for i = 1 : 10
a{i,1} = randn(200,5);
end
% Transform first five cells in one big matrix
c = cat(2,(a{1:5}));
n = size(a{1} , 2);
b = cell(5,1);
for j =1:5
% Take one column every 5 (or every "n" in general)
b{j} = c(: , 1:n:end );
end
I have a matrix as shown in the image. In this matrix if any of the values in one row is found in another row we remove the shorter row. For example row 2 to row 5 all contain 3, therefore I want to keep only row 5(the row with most non-zero values) and remove all other rows...please suggest a solution.
Thanks
I believe the below code should work. The idea is to sort the matrix first according to the number of elements in the rows, then loop and remove the rows that have matches. Probably not the most efficient code but should work in principle.. see the comments for more explanation
% generating the data
M = zeros(6, 10);
M(2,1:3) = [3 8 10];
M(3,1:4) = [3 8 10 9];
M(4,1:5) = [3 8 10 9 7];
M(5,1:6) = [3 8 10 9 7 4];
M(6,1) = [5];
% sorting according to the number of non-zero elements
nr_of_nonzero = sum(M~=0, 2);
[~, sort_indices] = sort(nr_of_nonzero);
M_sorted = M(sort_indices,:);
M_sorted(M_sorted==0)=NaN; % should not compare 0s (?)
% get rid of the matches
for i=1:size(M_sorted, 1)-1
for j=(i+1):size(M_sorted, 1)
[C,ia,ib] = intersect(M_sorted(i,:),M_sorted(j,:));
if numel(C)>0
M_sorted(i,:) = NaN;
end
break;
end
end
% reorder
M(sort_indices,:) = M_sorted;
% remove all NaN rows
M(all(isnan(M),2),:) = [];
% back to 0s
M(isnan(M)) = 0;
I'm not doing all the code here, but here's the steps that I would take to solve it. You will likely have to try different ways of doing it to obtain the intended result (i.e. vector operations, while loop, for loop, etc.).
Problem
Rows are repetitive and need to be reduced in a more compact form.
Solution
Look up mat2str.
Convert your vectors (rows) to strings. This can be done with temporary values like tmpstr1 = mat2str(yourMatrix(rowToBeCompared, :));
Parse the first string from beginning to end, while parsing the second string in the same way to make comparisons.
use strcmp to see if the string characters (or strings themselves) are the same: http://www.mathworks.com/help/matlab/ref/strcmp.html
Delete a row if you find it appropriate with yourMatrix[rowToDelete, : ] = [];
Try that and see if it works.
Note - Expansion of step 3:
if we have variable a = '[ab+11]';, we can select individual characters from the string like:
a(4)
ans = '+'
a(5)
ans = '1'
a(1)
and = '['
Therefore, you can parse the string with a loop:
for n = 1 : length(a)
if a(n) == '1' || a(n) == '0'
str(n) = a(n);
end
end
Like Sardar Usama said, it's helpful to provide the code so that we can copy and paste into our own MATLAB workspaces.
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'm currently working on creating a histogram of Altitudes at which a type of atmospheric instability happens. To be specific, it is when the values of what we call, N^2 is less than zero. This is where the problem comes in. I am trying to plot the occurrence frequency against the altitudes.
load /data/matlabst/DavidBloom/N_square_Ri_number_2005.mat
N_square(N_square > 0) = 0;
N_square = abs(N_square);
k = (1:87);
H = 7.5;
p0 = 101325;
nbins = (500);
N_square(N_square==0)=[];
Alt = zeros(1,578594);
PresNew = squeeze(N_square(:,:,k,:));
for lati = 1:32
for long = 1:64
for t = 1:1460
for k = 1:87
Alt(1,:) = -log((PresNew)/p0)*H;
end
end
end
end
So, let me explain what I am doing. I'm loading a file with all these different variables. Link To Image This shows the different variables it displays. Next, I take the 4-D matrix N_square and I filter all values greater than zero to equal 0. Then I take the absolute value of the leftover negative values. I then define several variables and move on to the next filtering.
(N_square(N_square==0)=[];
The goal of this one was give just discard all values of N_square that were 0. I think this is where the problem begins. Jumping down to the for loop, I am then taking the 3rd dimension of N_square and converting pressure to altitude.
My concern is that when I run this, PresNew = squeeze(N_square(:,:,k,:)); is giving me the error.
Error in PlottingN_2 (line 10)
PresNew = squeeze(N_square(:,:,k,:));
And I have no idea why.
Any thoughts or suggestions on how I could avoid this catastrophe and make my code simpler? Thanks.
When you remove random elements from a multi-dimensional array, they are removed but it can no longer be a valid multi-dimensional array because it has holes in it. Because of this, MATLAB will collapse the result into a vector, and you can't index into the third dimension of a vector like you're trying.
data = magic(3);
% 8 1 6
% 3 5 7
% 4 9 2
% Remove all values < 2
data(data < 2) = []
% 8 3 4 5 9 6 7 2
data(2,3)
% Index exceeds matrix dimensions.
The solution is to remove the 0 values after your indexing (i.e. within your loop).
Alt = zeros(1,578594);
for lati = 1:32
for long = 1:64
for t = 1:1460
for k = 1:87
% Index into 4D matrix
PresNew = N_square(:,:,k,:);
% NOW remove the 0 values
PresNew(PresNew == 0) = [];
Alt(1,:) = -log((PresNew)/p0)*H;
end
end
end
end
I have the data of the following form in a text file
Userid Gameid Count
Jason 1 2
Jason 2 10
Jason 4 20
Mark 1 2
Mark 2 10
................
.................
There are a total of 81 Gameids and I have around 2 million distinct users.
What I want is to read this text file and create a sparse matrix of the form
Column 1 2 3 4 5 6 .
Row1 Jason 2 10 20
Row2 Mark 2 10
Now I can load this text file in matlab and read the users one by one, reading their count and initializing the sparse array. I have tried this, it takes 1 second to initialize the row of one user. So for a total of 2 million users, it will take me a lot of time.
what would be the most efficient way to do this?
Here is my code
data = sparse(10000000, num_games);
loc = 1;
for f=1:length(files)
file = files(f).name;
fid = fopen(file,'r');
s = textscan(fid,'%s%d%d');
count = (s(:,2));
count = count{1};
position = (s(:,3));
position = position{1};
A=s{:,1};
A=cellstr(A);
users = unique(A);
for aa = 1:length(Users)
a = strfind(A, char(Users(aa)));
ix=cellfun('isempty',a);
index = find(ix==0);
data(loc,position(index,:)) = count(index,:);
loc = loc + 1;
end
end
Avoid the inner loop by usingunique once more for GameID.
Store the user names, because in your original code you can't tell which name - relates to each row. The same thing for game IDs.
Make sure to close the file after opening it.
sparse matrix does not support 'int32' you need to store your data as double.
% Place holders for Count
Rows = [];
Cols = [];
for f = 1:length(files)
% Read the data into 's'
fid = fopen(files(f).name,'r');
s = textscan(fid,'%s%f%f');
fclose(fid);
% Spread the data
[U, G, Count{f}] = s{:};
[Users{f},~, r] = unique(U); % Unique user names
[GameIDs{f},~,c] = unique(G); % Unique GameIDs
Rows = [Rows; r + max([Rows; 0])];
Cols = [Cols; c + max([Cols; 0])];
end
% Convert to linear vectors
Count = cell2mat(Count');
Users = reshape([Users{:}], [], 1);
GameIDs = cell2mat(GameIDs');
% Create the sparse matrix
Data = sparse(Rows, Cols, Count, length(Users), length(GameIDs), length(Count));
The Users will contain be the Row header (user names) and GameIDs the Column header.