Assembly of matrices using for loop

4 次查看（过去 30 天）
Silver
Silver 2018-8-31
评论： Silver 2018-9-6
I have 20 excel files containing matrix, each matrix has 49 columns (all the matrix has the same number of columns) and a variable number of lines (the number of lines is not always the same for all the matrix I have). I want to assemble all of them in one excel file , what makes a new matrix with 49 columns.This should not be addition but assembly. For exemple if I have these two matrix : A = [1 2;3 4] B = [5 6;7 8] The result I wish to have is a new matrix C while : C =
1 2
3 4
5 6
7 8
In other words it is sort of like joining the matrices but by adding each matrix to the previous one, successively from the line where the previous matrix has stopped while keeping the same number of columns (49).
Any idea how to do this? Thanks in advance
  2 个评论
madhan ravi
madhan ravi 2018-8-31
编辑：madhan ravi 2018-8-31
C=[A;B] this will give the result for the example?
Silver
Silver 2018-9-1
Thank you for answering.It does for this exemple, but for larger amounts of data, I need to use the For loop, and that's the problem.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

James Tursa
James Tursa 2018-8-31
Read each individual file into a cell array element, then vertically concatenate the cells all at once.
  2 个评论
Silver
Silver 2018-9-1
Thank you James Tursa for answering. However I would like to know when you said "Read each individual file into a cell array element" Does this script work ?
for i=1:data_ver %data_ver is the nmber of line (size) of the matrix
for j=1:data_hor %data_hor is the nmber of columns(size) of the matrix
temp = cell2mat(cellstr(Data(i,j))) ; %fill matrix
A(i,j)=str2double(temp) ;
end
end
And what about "vertically concatenate the cells all at once" I dont see what that means. Thank you again.
Stephen23
Stephen23 2018-9-1
编辑：Stephen23 2018-9-1
@Silver: you do not need to use any loops, as MATLAB's file importing functions are quite capable of importing the entire file by themselves. Also importing the data as character and then using str2double is most likely a misdirection: MATLAB's file importing function already import numeric data as numeric. So none of your code is very useful, or a good way to approach this task. A much better approach is to read the documentation:
https://www.mathworks.com/help/matlab/standard-file-formats.html
and pick a suitable method for reading your files.
"And what about "vertically concatenate the cells all at once" I dont see what that means"
Once you have all of the imported numeric data into one cell array, after the loop you can vertically concatenate the imported data into one matrix, exactly as you requested, e.g.:
mat = vertcat(C{:})

请先登录，再进行评论。

更多回答（1 个）

Stephen23
Stephen23 2018-9-1
编辑：Stephen23 2018-9-1
Following the examples in the MATLAB documentation:
https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html
N = 20;
C = cell(1,N);
for k = 1:N
F = sprintf('file%d.txt', k);
C{k} = importdata(F);
end
out = vertcat(C{:})
Or use dir, as shown in the link I gave above.
  8 个评论
显示 6更早的评论
Silver
Silver 2018-9-5
You rock !! Thank you so much it works, and thanks for explanation , appreciate that!
Silver
Silver 2018-9-6
It really helps me ! thank you again , For sure I've accepted the answer and flagged it ^^

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Programming 的更多信息

标签

产品


版本

R2017a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by