This is my first time posting so i hope you can help me. I am trying to write a function in matlab.
I have laded data from a file into a cell array. First column contains statements and the second contains T for true og F for false. I now want to split this array into a cell array with the statements and a logical vector with 1 for True and -1 for false.
I use the fgetl within a loop to read all the lines into the cellarray
Try to write it a bit more neatly next time, and consider including a small example.
Here is what you seem to be looking for:
Suppose you have a matrix M and want to split that into M_true and M_false
M = {1,'T';
22,'F';
333,'T'}
idx_T=strcmp(M(:,2),'T')
M_true = M(idx_T,1)
M_false = M(~idx_T,1)
Related
I want to assign part of a matrix into another matrix using a for loop in MATLAB. I've tried different ways but none of them worked. I want to know what's wrong with this one:
fullGrid = complex(zeros(FFTLen, numSym, numTx),zeros(FFTLen, numSym, numTx));
for i=0:(numSym/2)-1
for j=0:(FFTLen/2)-1
A(i,j)=[fullGrid(i,j)];
end
end
You made a very basic mistake. The index position in a matrix/array in
Matlab starts from 1 and not 0. So replace all the for loops from 1 to
required length.
Corrected code is given below.
fullGrid = complex(zeros(FFTLen, numSym, numTx),zeros(FFTLen, numSym, numTx));
for i=1:(numSym/2)-1
for j=1:(FFTLen/2)-1
A(i,j)=[fullGrid(i,j)];
end
end
I have two different sets of arrays within an array, which I called:
y={...}; % cell array of 1x1, with a 26x1 cell array within it.
Only_Data={...} %cell array of 525x1, with 525 different 1x12 cell arrays
The data that's within the arrays is string. I want to concatenate these two arrays into one and print that final result into a .txt file. But I'm having problems doing the last part.
This is what I've done for that purpuse:
new_subject3=[y; Only_Data];
new_subject3;
outfile='mynewfile';
filename=[outfile,'.txt'];
fid=fopen(filename,'w');
[nrows,ncols] = size(new_subject3);
for row = 1:nrows
fprintf(fid ,'%s\n', new_subject3{row}{1:end});
end
fclose(fid);
For some reason I'm not aware of, it only prints the 'y' array, but doesn't print anything from the 'Only_Data' array. Why would that be? I'm clueless. I'm sure it's not about the type of data, but further than that I don't know.
I'll be glad to learn how to do this, thanks in advance.
I have several arrays that are calculated example a,b and c (there are more than three) are calculated: Please note this is just an example the numbers are much larger and are not so basic
a=[1,2,3,4,5] b=[10,20,30,40,50] c=[100,200,300,400,500] and I want a for loop that inserts zeros into it so I can have the new_abc array steps look like.
1st for loop step new_abc=[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
2nd for loop step new_abc=[1,0,0,2,0,0,3,0,0,4,0,0,5,0,0]
3rd for loop step new_abc=[1,10,0,2,20,0,3,30,0,4,40,0,5,50,0]
4th for loop step new_abc=[1,10,100,2,20,200,3,30,300,4,40,400,5,50,500]
how can I do this with a for loop?
I started with the code below which gives me the zeros
a=[1,2,3,4,5]
new_abc=zeros(1,length(a)*(3));
But I'm not sure how to place the values of the array a b and c using a for loopinto the correct locations ofnew_abc
I know I could place all the arrays into one large array and do a reshape but the calculated arrays I use become to large and I run out of ram, so reading / calculating each array and inserting them into one common array new_abcusing a for loop works best.
I'm running octave 3.8.1 which is like matlab.
This should do it. You can put a,b,c into a cell array. (you can also put them in a matrix...)
new_abc = zeros(1, 3*numel(a));
in = {a, b, c};
for k = 1:3
new_abc(k:3:end) = in{k};
end
I am trying to create a string array which will be fed with string values read from a text file this way:
labels = textread(file_name, '%s');
Basically, for each string in each line of the text file file_name I want to put this string in 10 positions of a final string array, which will be later saved in another text file.
What I do in my code is, for each string in file_name I put this string in 10 positions of a temporary cell array and then concatenate this array with a final array this way:
final_vector='';
for i=1:size(labels)
temp_vector=cell(1,10);
temp_vector{1:10}=labels{i};
final_vector=horzcat(final_vector,temp_vector);
end
But when I run the code the following error appears:
The right hand side of this assignment has too few values to satisfy the left hand side.
Error in my_example_code (line 16)
temp_vector{1:10}=labels{i};
I am too rookie in cell strings in matlab and I don't really know what is happening. Do you know what is happening or even have a better solution to my problem?
Use deal and put the left hand side in square brackets:
labels{1} = 'Hello World!'
temp_vector = cell(10,1)
[temp_vector{1:10}] = deal(labels{1});
This works because deal can distribute one value to multiple outputs [a,b,c,...]. temp_vector{1:10} alone creates a comma-separated list and putting them into [] creates the output array [temp_vector{1}, temp_vector{2}, ...] which can then be populated by deal.
It is happening because you want to distribute one value to 10 cells - but Matlab is expecting that you like to assign 10 values to 10 cells. So an alternative approach, maybe more logic, but slower, would be:
n = 10;
temp_vector(1:n) = repmat(labels(1),n,1);
I also found another solution
final_vector='';
for i=1:size(labels)
temp_vector=cell(1,10);
temp_vector(:,1:10)=cellstr(labels{i});
final_vector=horzcat(final_vector,temp_vector);
end
I have some which converts a cell array of strings into a cell array of characters.
Note. For a number of reasons, both the input (C) and the output (C_itemised) must be cell arrays.
The cell array of strings (C) is as follows:
>> C(1:10)
ans =
't1416933446'
''
't1416933446'
''
't1416933446'
''
't1416933446'
''
't1416933446'
''
I have only shown a portion of the array here. In reality it is ~28,000 rows in length.
I have some code which does this, although it is very inefficient. The cellstr function takes up 72% of the code's time, as it is currently called thousands of times. The code is as follows:
C_itemised=cell(length(C),500);
for i=3:length(C)
temp=char(C{i});
for j=1:length(temp)
C(i-2,j)=cellstr(temp(j));
end
end
I have a feeling that some minor modifications could take out the inner loop, thus cutting down the overall running time substantially. I have tried a number of ways to do this, but I think I keep getting confused about whether to use {} or (), and haven't been able to find anything online that can help me. Can anyone see a way to make the code more efficient?
Please also note that this function is used in conjunction with other functions, and does work, although it is running slower than would be ideal. Therefore, I do not wish to change the format of C_itemised.
EDIT:
(A sample of) the output of my current function is:
C_itemised(1,1:12)
ans =
Columns 1 through 12
't' '1' '4' '1' '6' '9' '3' '3' '4' '4' '6' []
One thing I can suggest is to use the undocumented function sprintfc. This function is hidden from normal use in MATLAB, but it is used internally with a variety of other functions. Mainly, if you tried doing help sprintfc, it'll say that there's no function found! It's cool to sniff around the source sometimes!
How sprintfc works is that you provide it a formatting string, much like printf, and the data you want printed. It will take each individual element in the data and place them into individual cell arrays. As an example, supposing I had a string D = 'abcdefg';, if we did:
out = sprintfc('%c', D);
We get:
>> celldisp(out)
out{1} =
a
out{2} =
b
out{3} =
c
out{4} =
d
out{5} =
e
out{6} =
f
out{7} =
g
As such, it takes each element in your string and places them as individual characters serving as individual elements in a new cell array. The %c formatting string means that we want to print a single character per element. Check out the link to Undocumented MATLAB that I posted above if you want to learn more!
Therefore, try simplifying your loop to this:
C_itemised=cell(length(C));
for i=1:length(C)
C_itemised{i} = sprintfc('%c', C{i});
end
C_itemised will be a cell array, where each element C_itemised{i} is another cell array, with each element in this cell array being a single character that is composed of the string C{i}.
Minor Note
You said you were confused about {} and () in MATLAB for cells. {} is used to access individual elements inside the cell. So doing C{1} for example will grab whatever is stored in the first element of the cell array. () is used to slice and index into the cells. For example, if you wanted to make another cell array that is a subset of the current one, you would do something like C(1:3). This will create a three element cell array which is composed of the first three cells in C.