How can I create a fullpath from images of different subfolders?

Question

FSh 2019-7-24

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评论： Rik 2021-1-25

I have images with repitative names in diffrent folders, I want to read them all and use imread. The problem is when I use dir it creates diffrent columns but when i want to create a full path the result is 0.

*******************

 path = 'C/..../mainfolder/'];
country= ....
files=dir([datapath 'run','*',country,'.png'])
for k= 1:length(files)
t= strcat(files(k).folder,files(k).name)
end

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Answer 1

Stephen23 2019-7-24

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编辑：Stephen23 2019-7-28

在 MATLAB Online 中打开

Do not use path as a variable name (you shadow the inbuilt function of that name).

Do not concatenate strings to build paths.

Use fullfile instead, e.g.:

pattern = sprintf('run*%s.png',country)
files = dir(fullfile(datapath,pattern))

and

fullfile(files(k).folder,files(k).name)

Note that

C/

is unlikely to resolve to anything useful on any OS.

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FSh 2019-7-26

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%activity= 'run' or 'dart'
year1 = 1980
year2= 2010
for num= year1:year2 
        switch activity 
            case 'Indai'  
            path = ['C\folder\competition\run','\',num2str(num),'\']; % get images with this name from all subfolders 
            if strcmp(age,'rd')                     
                ag = 'old';
                list_images= dir([datapath 'run_',num2str(d),'*_',country,ag,'.png'])
            elseif strcmp(age,'rs')                    %German
                ag = '';
                list_images=dir([path 'run_',num2str(d),'*_',country,ag,'.png']);% get images with this name from all subfolders 
            end
            ti = 1;
        case 'Africa'
                path = ['C\folder\competition\dart','\',num2str(num),'\'];            
                list_images=dir([datapath 'dart',country,'_',num2str(d),'*.png'])% get images with this name from all subfolders 
            ti = 2;
end
 for i=1:length(images)
           filename = strcat(images(i).folder,'/',images(i).name);% Concatenate strings horizontally to create a full path
           I= imread(filename);% fo further process of showing image a series 
 end

it can not give me in "list_images" all the images of the requested names for all the years.

Walter Roberson 2019-7-26

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filedir = fullfile('C:', 'folder', 'competition', 'run', sprintf('%d',num));
if strcmp(age, 'rd')
   ag = 'old';
  list_images = dir(filedir, sprintf('run_%d*_%s%s.png', d, country, ag))
elseif strcmp(age, 'rs')
   ag = '';
   list_images = dir(filedir, sprintf('run_%d*_%s%s.png', d, country, ag))
end

You were using C\ instead of C:

You were defining path but using datapath instead.

It is cleaner to use fullfile() rather than string concatenation.

Stephen23 2019-7-28

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Walter Roberson also forgot to use fullfile (note that dir only accepts one input argument):

filedir = fullfile('C:', 'folder', 'competition', 'run', sprintf('%d',num));
if strcmp(age,'rd')
   ag = 'old';
elseif strcmp(age,'rs')
   ag = '';
else
    % ? what to do ?
end
list_images = dir(fullfile(filedir, sprintf('run_%d*_%s%s.png', d, country, ag)));

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Answer 2

Jon 2019-7-24

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编辑：Jon 2019-7-24

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Its not quite clear from the snippet of code and description you give but I think your problem is that you are not constructing the path to your files correctly. Note that if the path is incorrect and no files will be found then executing

files=dir([datapath 'run','*',country,'.png'])

will return

files =

0×1 empty struct array with fields:

name

folder

date

bytes

isdir

datenum

Which I think maybe is what you mean by the "result is 0"

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Jon 2019-7-26

编辑：Jon 2019-7-26

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I looked at your comments and I'm still not really clear what your exact directory structure is. Anyhow, a few comments.

First, I would recommend not using "path" as a variable name , path is very important MATLAB function that returns the current search path. If you use it as a local variable name, then that definition takes precedence and path command will no longer work.

That aside, I also noticed that while you assign the variable path, you don't alway use the value you assign to it. So for example

path = ['C\folder\competition\run','\',num2str(num),'\']; % get images with this name from all subfolders 
            if strcmp(age,'rd')                     
                ag = 'old';
                list_images= dir([datapath 'run_',num2str(d),'*_',country,ag,'.png'])
            elseif strcmp(age,'rs')                    %German
                ag = '';
                list_images=dir([path 'run_',num2str(d),'*_',country,ag,'.png']);% get images with this name from all subfolder

you assign the variable path, but then you don't use it if strcmp(age,'rd'), instead you use datapath

I'm not sure where datapath is assigned, so it is hard to know if it is assigned to the path you want.

Also I don't understand your final loop

 for i=1:length(images)
           filename = strcat(images(i).folder,'/',images(i).name);% Concatenate strings horizontally to create a full path
           I= imread(filename);% fo further process of showing image a series 
 end

I don't see where you have ever assigned the variable images, that you reference "images(i).folder". It seems like you should be using list_images instead.

In general, I would recommend stepping through your code with the debug tool and examining the values that you are assigning to the paths to see if they make sense.

FSh 2019-7-26

在 MATLAB Online 中打开

Thank you for your time, yes I had some mistake to put the right code here.

The problem is with the first for-loop, instead of listing the pictures from different years(subfolders), it just gives the last year 2010. not any other previous years.

%activity= 'run' or 'dart'
year1 = 1980
year2= 2010
for num= year1:year2 
        switch activity 
            case 'Indai'
%    dpath= ['C\folder\competition\run\1980\run_19800101_India_old.png'] 
%  images with other month and date in 1980 folder are here.
%    dpath= ['C\folder\competition\run\1981\run_19810401_India_old.png']       
%  the next folder with a list of images with other month and date in 1981 .
%  this will be continued till the last folder 2010
            dpath= ['C\folder\competition\run','\']
            dpath = [dpath,num2str(num),'\']; % get images with this name from all subfolders 
            if strcmp(age,'rd')                     
                ag = 'old';
                list_images= dir([dpath 'run_',num2str(d),'*_',country,ag,'.png'])
            elseif strcmp(age,'rs')                    %German
                ag = '';
 %  dpath= ['C\folder\competition\run\1980\run_19800101_India.png'] more than 100 folder with date changing
                list_images=dir([path 'run_',num2str(d),'*_',country,ag,'.png']);% get images with this name from all subfolders 
            end
            ti = 1;
        case 'Africa'
 %  dpath= ['C\folder\competition\dart\1980\run_19800102_Africa.png'] more than 100 folder with date changing
%   in between other images 
 %  dpath= ['C\folder\competition\dart\2002\run_20020102_Africa.png'] more than 100 folder with date changing
                dpath = ['C\folder\competition\dart','\',num2str(num),'\'];            
                images=dir([dpath 'dart',country,'_',num2str(d),'*.png'])% get images with this name from all subfolders 
            ti = 2;
end
 for i=1:length(images)
           filename = strcat(images(i).folder,'/',images(i).name);% Concatenate strings horizontally to create a full path
           I= imread(filename);% fo further process of showing image a series 
 end

Jon 2019-8-9

I understand from your comment that you still have not solved your problem. If you would like further help, please try to make a self contained example (a short script along with any necessary data files for it to run) that demonstrates the problem you are encountering. Also copy and paste the full text of the error messages you encounter when you try to run your example.