I have tried to import several csv files into one file. However, the new file overwrites the "original" ones.
Only the last processed one among them was imported. Something may be wrong about the loop, but I don't know where to change.
This is what I have:
p=dir('C:\foldername\*.csv');
for i=1:length(p)
[num, text, all]= xlsread(['C:\foldername\', p(i).name]);
end
You are overriding the variables in the loop.
Try to collect everything in cell array:
num = {};
text = {};
all = {};
p=dir('C:\foldername\*.csv');
for i=1:length(p)
[num{end+1}, text{end+1}, all{end+1}]= xlsread(['C:\foldername\', p(i).name]);
end
You cannot read all the things into the same variables, but you can put them in different dimensions.
p=dir('C:\foldername\*.csv');
num = cell(size(p));
text = cell(size(p));
all = cell(size(p));
for i=1:length(p)
[num{i}, text{i}, all{i}]= xlsread(['C:\foldername\', p(i).name]);
end
Related
I would like to read a particular variable AandB_cossy from N Matlab files. To do this I have used as below. To read the values, we generally use Noplate1.AandB_cossy(:,1). This works fine. My doubt is once I assign to Noplate1, Noplate2, Noplate3, how do I read without specifying the AandB_cossy again to read the values for each one? Is it possible to do something like Noplate1.var(:,1)?? Any help is highly appreciated. Thanks a lot.
clearvars; close all; clc;
var='AandB_cossy';
Noplate1=load('dummy1.mat',var);
Noplate2=load('dumsabs2.mat',var);
Noplate3=load('yipposbn123.mat',var);
You can use var to index into the struct Noplate1 as follows:
var = 'AandB_cossy';
Noplate1 = load('dummy1.mat',var);
Noplate1.(var)(:,1);
To read many files, the easiest is to list their names in a list (you can use the function dir to generate this list if it is all files in a directory, for example). Then you iterate over the list and read the values into a cell array:
fnames = {'dummy1.mat','dumsabs2.mat','yipposbn123.mat'};
var = 'AandB_cossy';
Noplate = cell(size(fnames));
for ii = 1:numel(fnames)
tmp = load(fnames{ii},var);
Noplate{ii} = tmp.(var);
end
Now you can access each data array as Noplate{1}, Noplate{2}, etc.
I am beginner in MATLAB. I would like to load 200 image files (size 192x192) in a specific folder by using a for loop.
The image names are '1.png', '2.png', '3.png' and so on.
My code is as below.
list = dir('C:/preds/*.png');
N = size(list,1);
sum_image = zeros(192,192,200);
for i = 1:N
sum_image(:,:,i) = imread('C:/preds/i.png');
end
Which part should I change ?
I would probably do it like the code below:
You are currently getting the list of filenames then not really doing much with it. Iterating over the list is safer otherwise if there is a missing number you could have issues. Also, the sort maybe unnecessary depending if you image numbering is zero-padded so they come out in the correct order ... but better safe than sorry. One other small change initializing the array to size N instead of hard-coding 200. This will make it more flexible.
searchDir = 'C:\preds\';
list = dir([searchDir '*.png']);
nameList = {list.name}; %Get array of names
imNum = str2double(strrep(nameList,'.png','')); %Get image number
[~,idx] = sort(imNum); %sort it
nameList = nameList(idx);
N = numel(nameList);
sum_image = zeros(192,192,N);
for i=1:N
sum_image(:,:,i) = imread(fullfile(searchDir,nameList{i}));
end
I would suggest changing the line within the loop to the following:
sum_image(:,:,i) = imread(['C:/preds/', num2str(i), '.png']);
MATLAB treats the i in your string as a character and not the variable i. The above line of code builds your string piece by piece.
If this isn't a homework problem, the right answer to this question is don't write this as a for loop. Use an imageDatastore:
https://www.mathworks.com/help/matlab/ref/imagedatastore.html
ds = imageDatastore('C:/preds/');
sumImageCellArray = readall(ds);
sumImage = cat(3,sumImageCellArray{:});
myFiles = 1x7 cell
when I try
for m =1:numel(myFiles )
fil{m} = dir(myFiles {m});
fil{m}.bytes ;
end
This is not working
I got the error :
function is not defined for 'cell' inputs.
First of all you should mention the error message you get.
Now, besides that are some obvious problems:
myFiles {ii}
This is not valid syntax to index into a cell array. Perhaps removing the space helps.
Furthermore you loop over m and then use ii as an index.
Lastly you assign to fil everytime. In practice this means only the last result is stored. Perhaps assigning to fil(m) would suit your needs better.
The command dir will show you the content of a folder. As your variable is named "myFiles" I assume it contains filenames and not foldernames. So I think you're rather looking for a loop like this:
for ii = 1:numel(myFiles)
fil{ii} = which( myFiles{ii} )
end
which gives you an array with the full paths to your files. Or are you looking for the folders containing the files in "myFiles"? Then you can use:
for ii = 1:numel(myFiles)
fil{ii} = fileparts( which( myFiles{ii} ) )
end
returning you the corresponding folders.
regarding your comments:
the existence of the files/folders in "myFiles" is the only purpose?
Then you could do that:
for ii = 1:numel(myFiles)
fil(ii) = exist( which(myFiles{ii}), 'file' );
end
existMyFiles = logical(fil);
returning a logical array specifying the existence of your files.
I am trying to cycle through a list of variables I have say 30+ and calculate the maximum and minimum value for each column in each variable. Save this in a new array and then export to excel.
My thoughts were to use the who function to create an array with the name of all variables which are present. Then cycling through each one using a for loop after working out the size of the array which was created. This works fine, however when I try and use the string to reference the array it does not work.
I will add in the code which I have written hopefully someone will be able to come up with an easy solution :).
variable_list = who
cell2 = input('What cell size do you want to look at? ');
STARTcell = input('What was the start cell size? ');
[num_variables, temp] = size(variable_list);
for va = 1:num_variables
variable = variable_list{va}
[max_value, max_index] = max(variable{cell2/STARTcell})
[min_value, min_index] = min(variable{cell2/STARTcell})
format_values{va} = vertcat(max_values, max_index, min_value, min_index);
end
The variables I am looking at are arrays which is why I use the cell2/STARTcell to reference them.
You need to use the eval() function to be able to get the value of a variable corresponding to a string. For example:
a = 1;
b = 2;
variable_list = who;
c = eval(variable_list{2});
results in c being 2. In your code, the following line needs to change from:
variable = variable_list{va}
to:
variable = eval(variable_list{va});
resulting in variable having the value of the variable indicated by the string variable_list{va}. If variable is of cell type, then you should be fine, otherwise you may have to revise the next two lines of code as well because it seems that you are trying to access the content of a cell.
I need to output .mat files for the below data. I need one file to have cell (1,1) to be Mean_RPM_list1, cell (2,1) to be Mean_RPM_list2 etc. And then I need another file to have cell(1,1) to be Mean_Torque_list1 to have cell(1,1).....and so on.
Can anybody shed any light on this for me?
Also if someone knows how to automate me calling the matrices A and B so I could have A = [Mean_rpm1:Mean_rpmMAX], that would also be very helpful.
TIA for any help.
A = [Mean_rpm1 Mean_rpm2 Mean_rpm3 Mean_rpm4 Mean_rpm5 Mean_rpm6 Mean_rpm7 Mean_rpm8 Mean_rpm9 Mean_rpm10 Mean_rpm11 Mean_rpm12];
B = [Mean_torque1 Mean_torque2 Mean_torque3 Mean_torque4 Mean_torque5 Mean_torque6 Mean_torque7 Mean_torque8 Mean_torque9 Mean_torque10 Mean_torque11 Mean_torque12];
plot(A,B,'*')
for i = 1:num_bins;
bin = first + ((i-1)/10);
eval(sprintf('Mean_RPM_list%0.f = A;',bin*10));
eval(sprintf('Mean_Torque_list%0.f = B;',bin*10));
end
First of all this is really bad idea to create a set of variables with names different by numbers. As you can see it's very difficult to deal with such variables, you always have to use eval (or other related) statements.
It's much easier to create a cell array Mean_rpm and access its elements as Mean_rpm{1}, etc.
If the vectors are numeric and have the same size you can also make a 2D/3D array. Then access as Mean_rpm(:,:,1) etc.
Next, to store a cell array to a mat-file you have to create this array in MATLAB. No options (at least for now) to do it by parts in a loop. (But you can do it for numeric vectors and matrices using matfile object.) So why do you need this intermediate Mean_RPM_list variable? Just do Mean_RPM_list{bin*10} = A in your loop.
For your first question, if you already have those variables you have to use eval in a loop. Something like
A = [];
for k=1:K
eval(sprintf('A{k} = [A, Mean_rpm%d];',k));
end
You can also get names for all similar variables and combine them.
varlist = who('Mean_rpm*');
A = cell(1,numel(varlist);
for k = 1:numel(varlist)
eval('A{k} = varlist{k};');
end
Here is one without loop using CELL2FUN:
A=cellfun(#(x)evalin('base',x),varlist,'UniformOutput',0);
You should avoid having all these individual variables around in the first place. Data types like arrays, cell arrays and structure arrays exist to help you with this. If you want each variable to be associated with a name, you can use a structure array. I've made an example below. Instead of assigning a value to Mean_rpm1 like you are doing now, assign it to meanStruct.Mean_rpm1 then save the entire structure.
% as you generate values for each variable, assign them to the
% appropriate field.
meanStruct.Mean_rpm1 = [10:10];
meanStruct.Mean_rpm2 = [12:15];
meanStruct.Mean_rpm3 = [13:20];
meanStruct.Mean_rpm4 = [14];
meanStruct.Mean_rpm5 = [15:18];
meanStruct.Mean_rpm6 = [16:20];
meanStruct.Mean_rpm7 = [17:22];
meanStruct.Mean_rpm8 = [18:22];
meanStruct.Mean_rpm9 = [19:22];
meanStruct.Mean_rpm10 = [20:22];
meanStruct.Mean_rpm11 = [21:22];
meanStruct.Mean_rpm12 = [22:23];
% save the structure array
save('meanValues.mat','meanStruct')
% load and access the structure array
clear all
load('meanValues.mat')
temp = meanStruct.Mean_rpm3