I am new to Matlab and was trying to concatenate array from cell arrays. I have done it as shown below.
S = load('input_file.mat');
c = struct2cell(S);
v = cell2mat(c(1,1));
temp = v(1:500,1:600);
v = cell2mat(c(3,1));
temp1 = v(1:500,1:600);
v = cell2mat(c(2,1));
temp2 = v(1:500,1:600);
v = cell2mat(c(4,1));
temp3 = v(1:500,1:600);
array1 = vertcat(temp,temp1);
array2 = vertcat(temp2,temp3);
But i guess there should be a better way or a direct function call which can get me the same result as i am getting from the code shown?
This is a very specific task, not very general, unless I'm missing the pattern. Starting after struct2cell:
C3 = cellfun(#(x)x(1:500,1:600),c,'uni',0);
array1 = vertcat(C3{[1 3]});
array2 = vertcat(C3{[2 4]});
Although, you could probably get rid of your initial structfun if you replace cellfun above with structfun, taking s as an input. It simply operates on each field.
Related
I am currently using MatLab R2014a
I have one array and one cell:
MyArray = ['AA1', 'AA2', 'AB1', 'AB2', 'Acc1', 'Acc2'];
MyCell = {'Name1AA1', 'Name2AA1', 'Name3Acc2', 'Name4AB2', 'Name5AD1};
MyArray consists of code names that are repeatable throughout MyCell.
I would like to check if any of the strings in MyArray are in MyCell and if it is, save the name to a new cell.
For now I have:
NewCell = {};
for i = 1:length(MyCell)
for j = 1:length(MyArray)
Find = strfind(MyCell(i), MyArray)
if ~isempty(Find)
NewCell = {NewCell; MyCell(j)}
end
end
end
However, when I use strfind I get this error message:
Undefined function 'strfind' for input arguments of type 'char'
If I use strcmp instead of strfind, I get an array of everything in MyCell repeated by the number of elements in MyArray.
My Ideal output would be:
NewCell1 = {'Name1AA1', 'Name2AA1'}
NewCell2 = {'Name4AB2'}
NewCell3 = {'Name3Acc2'}
ie, no new cell for the code names that are not present in MyArray or no new cell if there is a code name in MyArray but not in MyCell.
Any help is welcome, and thanks for your time
You can use a combination of regular expressions to achieve the desired output. Your approach of wanting to name variables dynamically is not recommended and will lead to code which is harder to debug. Use indexing instead.
You can read this informative post on Matlab's forum to understand why.
%Your input data.
MyArray = ['AA1', 'AA2', 'AB1', 'AB2', 'Acc1', 'Acc2'];
MyCell = {'Name1AA1', 'Name2AA1', 'Name3Acc2', 'Name4AB2', 'Name5AD1'};
%Find common elements between MyArray and MyCell.
elem = cellfun(#(x) regexp(MyArray,x(end-2:end),'match'),MyCell,'un',0);
%Eliminate duplicates.
NewCell = unique([elem{:}]);
%Find elements in MyCell which end with NewCell elements and group them.
NewCell = cellfun(#(x) regexp([MyCell{:}],strcat('Name\d\w?',x),'match'),NewCell,'un',0);
%Join elements.
NewCell{1} = {strjoin(NewCell{1},''',''')};
NewCell{1} = {'Name1AA1','Name2AA1'}
NewCell{2} = {'Name4AB2'}
NewCell{3} = {'Name3Acc2'}
I have a string :
A="ILOVEYOUMATLAB"
and I create 2 empty array:
B1=[]
B2=[]
when i used the while loop, for the first time looping, if i want the first character from the A to store in B1 array, what command i need to write?
if in Python, i just need to used append command, but if in Matlab, what is the commend need to apply?
If you have MATLAB R2016b or newer you can use the new string class' overloaded + operator to append text in a more pythonic manner:
A = 'hi';
B = "";
B = B + A(1)
Which gives you:
B =
"h"
Here I've created A as a traditional character array ('') and B as a string array (""), mainly to avoid having to index into the string array (A{1}(1) instead of A(1)).
You can also just use traditional matrix concatenation to accomplish the task:
B = [B, A(1)];
% or
B = strcat(B, A(1));
% or
B(end+1) = A(1);
Note that 4 of these approaches will continually grow B in memory, which can be a significant performance bottleneck. If you know how many elements B is going to contain you can save a lot of IO time by preallocating the array and using matrix indexing to assign values inside your loop:
A = {'apple', 'banana', 'cucumber'};
B = char(zeros(1, numel(A)));
for ii = 1:numel(A)
B(ii) = A{ii}(1);
end
you can try strcat for concatenating strings in matlab
https://www.mathworks.com/help/matlab/ref/strcat.html
Try using arrays instead of matrices. You can assign the first letter to the first position of the B1 array like this:
>> A = 'ILOVEMATLAB';
>> B1 = {};
>> B1{1} = A(1);
>> B1{1}
ans =
I
To Loop through:
for i = 1:length(A)
B1{i} = A{i};
end
I have a similar question to my previous one. This time the form of the nested structure looks like this:
Sizes = [2, 5, 8, 6, 3];
cells = 5;
for i = 1:cells
for j = 1:Sizes(i)
a(i).b.c(j).d = rand(1,1);
end
a(i).b.Size = Sizes(i);
end
Again I would like to put all the d values of a(:).b.c(:) into a single cell array that contains 1 x cells cells.
Here is my solution using cellfun but I would like to avoid this function:
ab = [a.b];
abc = {ab.c};
abcd = cellfun(#(x) [x.d], abc, 'UniformOutput', false);
Using the previous solution for abc:
abc = [ab.c];
creates a 1x24 struct array with field d. I thought of using the Size field to reshape this result into a cell array but I don't know how or if it is possible. Do you have a better appraoch without using loops and without cellfun?
You can do this using mat2cell as follows:
ab = [a.b];
abc = [ab.c];
abcd = mat2cell([abc.d], 1, [ab.Size]);
I have a vector/ or it could be array :
A = [1,2,3,4,5,1,2,3,4,5,1,2,3]
I want to extract existing different values/elements from this vector without repeating:
1,2,3,4,5
B= [1,2,3,4,5]
How can I extract it ?
I would appreciate for any help please
Try this,
A = [1,2,3,4,5,1,2,3,4,5,1,2,3]
y = unique(A)
B = unique(A) returns the same values as in a but with no repetitions. The resulting vector is sorted in ascending order. A can be a cell array of strings.
B = unique(A,'stable') does the same as above, but without sorting.
B = unique(A,'rows') returns the unique rows ofA`.
[B,i,j] = unique(...) also returns index vectors i and j such that B = A(i) and A = B(j) (or B = A(i,:) and A = B(j,:)).
Reference: http://cens.ioc.ee/local/man/matlab/techdoc/ref/unique.html
Documentation: https://uk.mathworks.com/help/matlab/ref/unique.html
The answers below are correct but if the user does not want to sort the data, you can use unique with the parameter stable
A = [1,2,3,4,5,1,2,3,4,5,1,2,3]
B = unique(A,'stable')
I'm trying to tidy up my code. I have an array with 5 columns, each of which is assigned to a variable. At present, I use:
x = inputData(i,1);
y = inputData(i,2);
currentSampleTime = inputData(i,3);
velocityX = inputData(i,4);
velocityY = inputData(i,5);
I thought I could tidy things up a bit by just doing the following:
[x y currentSampleTime velocityX velocityY] = inputData(i,:);
Apparently this does not work. I presume there must be an elegant solution?
If inputData was a cell array then you could do this:
[x y currentSampleTime velocityX velocityY] = deal(inputData{i,:});
However, since you are indexing the row with the variable i can I assume that this is inside a for loop?
If so I would just do the following before the loop?
x = inputData(:,1);
y = inputData(:,2);
currentSampleTime = inputData(:,3);
velocityX = inputData(:,4);
velocityY = inputData(:,5);
Then just use x(i) y(i) etc inside of your loop.
... or depending on how inputData is generated try to create the necessary arrays when reading in or creating inputData.
Also, on a personal note I don't like using i as a variable in m-code because it can easily get confused with the imaginary number if not properly initialized.
Try this:
wh = size(inputData);
temp = mat2cell(inputData,wh(1),ones(1,wh(2)));
[x,y,currentSampleTime,velocityX,velocityY] = deal(temp{:});