Export every third row from excel.

Hi all, I want to read the excel in matlab and get data of every third row from the first row till the end for all sheets. Each sheet is x and y data for 289 frames. I missed the last two rows of data so I also would like to round 289/3 up to the upper integer. Thank you so much.

[dpb]

So show us what you've done and where you had a problem...

>> ceil(289/3)
ans =
    97
>> 

[Yang Hu]

Hello, this is my code so far. I think it can output the data I want but I don't know how to export it to excel. x1, y1 are the new data I want to output.

close all

global mu

SPACE_UNITS = 'µm';

TIME_UNITS = 'min';

%% If loading in individual sheets

sheets = sheetnames('4.4.22.xlsx');

filename = '4.4.22_15mins'; %update filename to describe

f = 289;

for i=1:size(sheets)

xy=readmatrix('4.4.22.xlsx', 'Sheet',sheets(i), 'Range','A1:B289');

B=xy(~isnan(xy)); %takes out a defect

if size(B, 1)==f*2 % f*2

if i==1

x1=xy(:,1);

y1=xy(:,2);

else

x1=[x1; xy(:,1)];

y1=[y1; xy(:,2)];

end

end

end

%%reshape input x and y

x=reshape(x1, f, []);

y=reshape(y1, f, []);

%% manipulate data in 15 mins time gap

x1 = x(1:3:end,:); %get every third x coordinate

y1 = y(1:3:end,:); %get every third y coordinate

f1 = ceil(f/3);%round up to upper integer

Answer 1

[Voss]

sheet = 1;
data = zeros(97,0);
while true
    try
        new_data = readmatrix('4.4.22.xlsx','sheet',sheet);
    catch
        break
    end
    data(:,end+[1 2]) = new_data(1:3:end,:);
    sheet = sheet+1;
end
size(data)

ans = 1×2

97 66

[Yang Hu]

Thank you very much! I uploaded the code I adjusted in the upper comment.

[Voss]

You're welcome! To export x1 and y1:

writematrix([x1 y1],'result.xlsx')

That will give you all 33 columns of x1 followed by all 33 columns of y1. If you want it to be the first column of x1 followed by the first column of y1, then the second column of each, etc., probably you should modify your code to have them in a single variable. Then export using writematrix.

[Yang Hu]

I made it. Thank you for your help!

[Yang Hu]

Would you mind sharing me your learning experience of using matlab?

[Voss]

You're welcome!

[Voss]

@Yang Hu I didn't mean to ignore your question, I only saw it just now.

To answer: I learned MATLAB over several years, first using it for signal processing stuff in college and later at a job with a heavy MATLAB GUI development component (many years before AppDesigner was introduced). And I learn new aspects of it almost every day still, from seeing some of the creative answers here on this forum.

I don't have a specific reference I can point you to and say, this is how I learned MATLAB (although you may benefit from going through parts of the Onramp). I guess different people learn best through different methods, but for me the best way to learn anything is by trial-and-error: Try something and see what happens, if it doesn't work and you don't know why, read the documentation (if any) to find out. Keep trying things until: (1) you get something that works and you know why it works and under what conditions it will fail, or: (2) you realize that what you wanted to do is not feasible and you understand why, in which case the next step is to think of an alternative way to approach the problem. (Note that none of that is specific to learning MATLAB, but it applies just as it applies to any problem-solving activity - it's the scientific method after all.)