How to import column data from multiple Excel files with different number of rows?

I have n Excels files which I need to copy and store their data into Matlab. In each Excel file, the first column represents a specific variable, e.g., "Time", and the second column is another variable, e.g., "Displacement". Each of these Excel files has the same number of columns but different number of rows. For instance, file-1 has 100 rows, but file-2 has 150 rows. Using the code below (named PlotAll), I get the following error:

Subscripted assignment dimension mismatch.

Error in PlotAll

Time (:,K) =data(:,1);

How can I solve this error? I believe it's related to having an array which changes size in the "for" loop, but I don't know how to solve it.

Thanks,

clc
clear all
close all
fnames = dir('*.xls');
numfids = length(fnames);

for K = 1:numfids
data = xlsread(fnames(K).name);                                   
Time(:,K)=data(:,1);
Displacement(:,K)=data(:,2);
end

[Jan]

The brute clearing header "clc, clear all, close all" does not offer any benefits here. Therefore it is a cargo cult programming (link): It migt have been useful anywhere else, so repeat it, even if it does not have any meaning here. Beside this, it wastes a lot of time by removing all loaded functions from the memory. Reloading them from the slow disk is time-consuming.

[Jose Rubio]

Thanks for the advice, Jan.

Answer 1

[Fangjun Jiang]

Since each file contains different number of rows, you will need to use cell array for this. Change inside the loop to

Time{K}=data(:,1);
Displacement{K}=data(:,2);

It is better to pre-allocate before the loop

Time=cell(size(fnames));
Displacement=cell(size(fnames));

When using the data

plot(Time{K},Displacement{K})

[Jose Rubio]

Thanks Fangjun. This code works for me.

Answer 2

[Easwar Kumar Yarrabikki]

%%You can try something like this, Just finding the length of vector and defining the sizes

clc
clear all
close all
fnames = dir('*.xlsx');
numfids = length(fnames);
Time=[];
Displacement=[];
for K = 1:numfids
data = xlsread(fnames(K).name); 
row_length=length(data(:,1));
Time(1:row_length,K)=data(:,1);
row_length1=length(data(:,2));
Displacement(1:row_length1,K)=data(:,2);
end

[Jan]

Use size(data, 1) instead of length(data(:,1)), because the latter wastes time with creating a temporary vector only to count its elements. size can solve this directly.

[Jose Rubio]

Thanks for the quick response Easwar and Jan. This code works.

I followed Jan's suggestion and replace length(data(:,1)) with (data, 1) and it works as well.