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Creating a loop to receive data from multiple files

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I have 400 csv files, which contains the location of points and its temperature value. What I want to do is to build a command that calculate derivative dT/dx which are equally spaced from each csv file, receive the specific row that has the maximum derivative, and save the information of every 400 files in a single file. I would have done it if there are only about 10files, but for 400 files must be done with loops. Please help me. Thank you
  1 Comment
young jin Kwak
young jin Kwak on 13 Nov 2016
I think I am 80% all the way there, but cannot get the txt file with data for 421 files. If I run the following code, txt file takes the output only for sec, and rewrite it over and final output is only for last step. Please let me know what I have done wrong
format long
numfiles =421;
mydata = cell(1,numfiles);
for k = 1:numfiles
myfilename = sprintf('side20m0%d.csv',k-1); mydata{k} = cell(1,numfiles);
x_location = importfile(myfilename);
temp = importfile1(myfilename);
deriv = zeros(502,1);
for j=1:502
if j<502
deriv(j) = (temp(j+1)-temp(j))/(x_location(j+1)-x_location(j));
deriv(j) = 0;
M = [deriv,x_location];
[minA loc] = min(M(:,1));
xAtMin = zeros(420,1);
xAtMin(k) = M(loc,2);
fileID = fopen('Result.txt','w');
fprintf(fileID,'%6.6f\n', xAtMin(k));
fclose(fileID); end

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Answers (1)

Shivaputra Narke
Shivaputra Narke on 13 Nov 2016
Hey there, I am not understanding what is exactly stopping you to do this ? I guess, you are not doing it because of time constraint on processing 400 files (even through loop xlsread/csvread will take more time that depends upon the file size too).
Temp=[]; Locn=[]; for i=1:length(DataFiles) [Data,text,~]=xlsread(DataFiles{i}); % For e.g. in excel, column 4 contains temperature and column 5 contains location of points Temp(:,i)=Data(:,4); Locn(:,i)=Data(:,5); end
  1 Comment
young jin Kwak
young jin Kwak on 13 Nov 2016
Thank you for your help. I am really newbie in MATLAB. I made a example here. I have 400 files of csv as below. Each file indicate different time steps.(1.csv ~ 400.csv) What I want to do is for each time step, calculate the derivative dT/dx, (dx = same , equally distributed), and find the row that has maximum dT/dx, and save that specific location value with max derivative for each time steps. So output would be a single txt or csv file with 400rows. I can import a single data and calculate the value, but do not have any idea to do it for all 400 files. Thank you.

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