I am having a problem storing a 3 dimensional array into a proper format.
The text file reads as follows:
4 3 5 4 3 2
3 5 4 3 2 3
1 0 4 3 2 4
2 3
1 5
1 6
3 5
the integers are standard integers and need to be arranged as they appear. So the upper part of the txt file will be stored into a 3x3 matrix with each cell containing the two integer individual values. the bottom values should be stored in a 1x4 matrix with each cell containing the 2 individual integer values.
Related
I am doing some 3D and 4D matrix manipulation in Matlab.
I have created a 2D array which row values contain the index values of interest in a 3D matrix.
Assuming array A of size (Nx2)
A=[2 3 1;5 6 2;7 9 3;3 3 4;1 5 5]
2 3 1
5 6 2
7 9 3
3 3 4
1 5 5
Then, I want to use these elements to manipulate matrix B of size (NxMxL)
B=rand(9,9,5);
So I want to set B(2,3,1)=0 which corresponds to A(1,:).
If I naively go B(A(1,:))=0 this doesn't return me the desired output.
What I understand is that Matlab translate this into B=B(:) which reshape the matrix into a 1xNML
and then returns me the elements 2, 3 and 1 of the reshaped matrix.
How can I avoid this and make it understand my argument B(A(1,:))=B(2,3,1)?
use sub2ind , for example zeroing all the elements in B using of the rows in A as indices:
B(sub2ind(size(B),A(:,1),A(:,2),A(:,3)))=0;
I am working in EXCEL VBA.
I have a 2 dimensional array (for this example, let's say its a 5 x 5 one-based array). This is my raw data (Array "A"):
6 7 7 8 5
9 9 9 9 7
1 3 6 9 3
7 3 2 9 9
4 9 6 5 2
I also have a separate array whose row space mirrors that of the first (e.g., a 5 x 3 one-based array). The 1st column of this array is the row number of the raw data (A). This is my meta data (Array "B"):
1 0 0
2 1 0
3 0 0
4 0 0
5 1 0
For every occurrence of "1" in the 2nd column of the meta data array (B), I need to remove the corresponding row from my raw data array (A) AND add that row to a third array (Array "C")(which will not contain any data at the beginning of this process). Therefore, in this example, I need to remove rows 2 & 5 from Array A and place them in Array C.
I also need to copy the 1st column of the Array B (the original row numbers of Array A) to both arrays A & C so that after some further processing I can re-combine the results and return the data to its original order.
I'm not sure how best to go about this. Any suggestions?
Thanks!
I'm trying to reshape an array, perform an operation and then reshape it back to the original. See example of the output I'm trying to get. I can get a and b but I'm having trouble getting c to look like a again.
Step 1) (the original array)
1 1 1
2 2 2
3 3 3
4 4 4
5 5 5
Step 2) (reshape and perform some operation)
1,1,1,2,2,2,3,3,3,4,4,4,5,5,5
Step 3) (array is reshaped back to the original size to look like step 1) this is what I want
1 1 1
2 2 2
3 3 3
4 4 4
5 5 5
I can get the variables a and b but I'm not sure how to reshape c from b to look like a again see example code and output below
a=[repmat(1,[1,3]);repmat(2,[1,3]);repmat(3,[1,3]);repmat(4,[1,3]);repmat(5,[1,3])]
[rw,col]=size(a)
b=reshape(a',1,rw*col)
c=reshape(b,rw,col)
a=
1 1 1
2 2 2
3 3 3
4 4 4
5 5 5
b=1,1,1,2,2,2,3,3,3,4,4,4,5,5,5
c =
1 2 4
1 3 4
1 3 5
2 3 5
2 4 5
Ps: I'm using Octave 4.0 which is like Matlab.
MATLAB and Octave use column-major ordering so you'll need to reshape the result with that in mind. The data will be filled down the columns first but you want it to fill the columns first. To achieve this, you can specify the number of columns as the number of rows provided to reshape and then transpose the result
c = reshape(b, 3, []).'
Or more flexibly
c = reshape(b, flip(size(a))).'
I have a 2D matrix and want to sort rows and columns based on two other vectors i.e. one for ordering rows another for ordering columns in MATLAB
Example: A (Matrix to order)
0 1 2 3 4
1 1 8 9 7
2 3 4 6 2
3 1 2 0 8
Row Vector (Order for sorting rows of matrix A)
1
4
2
3
And column vector
1 5 4 2 3
Modified A
0 4 3 1 2
3 8 0 1 2
1 7 9 1 8
2 2 6 3 4
How about:
ModifiedA=A(RowVector,ColumnVector);
Note: Matab's indexing starts at 1 not at 0, adapt your indexing vectors accordingly.
In MATLAB, you can use the second output of sort to get the 1-based indexes that MATLAB is looking for (in this case you could have just added 1, but using sort works even if the row and column vectors are not consecutive).
[~,rowIdx] = sort(rowVector);
[~,colIdx] = sort(colVector);
And then you can apply the indexing operation to the matrix:
modifiedA = A(rowIdx, colIdx);
I have a 4-dimensional dictionary I made with a Python script for a data mining project I'm working on, and I want to read the data into Matlab to do some statistical tests on the data.
To read a 2-dimensional matrix is trivial. I figured that since my first dimension is only 4-deep, I could just write each slice of it out to a separate file (4 files total) with each file having many 2-dimensional slices, looking something like this:
2 3 6
4 5 8
6 7 3
1 4 3
6 6 7
8 9 0
This however does not work, and matlab reads it as a single continuous 6 x 3 matrix. I even took a look a dlmread but could not figure out how to get it do what I wanted. How do I format this so I can put 3 (or preferably more) dimensions in a single file?
A simple solution is to create a file with two lines only: the first line contains the target array size, the second line contains all your data. Then, all you need to do is reshape the data.
Say your file is
3 2 3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
You do the following to read the array into the variable data
fid = fopen('myFile'); %# open the file (don't forget the extension)
arraySize = str2num(fgetl(fid)); %# read the first line, convert to numbers
data = str2num(fgetl(fid)); %# read the second line
data = reshape(data,arraySize); %# reshape the data
fclose(fid); %# close the file
Have a look at data to see how Matlab orders elements in multidimensional arrays.
Matlab stores data column wise. So from your example (assuming its a 3x2x3 matrix), matlab will store it as first, second and third column from the first "slice", followed by the first, second third columns from the second slice and so on like this
2
4
3
5
6
8
6
1
7
4
3
3
6
8
6
9
7
0
So you can write the data out like this from python (I don't know how) and then read it into matlab. Then you can reshape it back into a 3x2x3 matrix and you'll retain your correct ordering.