while loop question number 2

Question

John 2013-4-16

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关闭： MATLAB Answer Bot 2021-8-20

My first question was answered, but wasn't a complete solution. Here's a portion of the data file:

 79, 970108,  1,    5,  0.088,  6.383,
 79, 970108,  1,   25,  0.075,  4.380,
 79, 970108,  1,   45,  0.094,  0.710,
 79, 970108,  1,   75,  0.221,  3.010,
 79, 970108,  1,  100,  0.140,  0.793,
 79, 970108,  1,  125,  0.094,  0.243,
 79, 970108,  1,  150,  0.054,  0.117,
 79, 970108,  1,  175,  0.022,  0.043,
 80, 970218,  1,    5,  0.097,  6.293,
 80, 970218,  1,   25,  0.096,  4.920,
 80, 970218,  1,   45,  0.094,  2.533,
 80, 970218,  1,   75,  0.125,  3.520,
 80, 970218,  1,  100,  0.198,  2.257,
 80, 970218,  1,  125,  0.222,  0.723,
 80, 970218,  1,  175,  0.072,  0.107,
 81, 970312,  1,    5,  0.091,  6.983,
 81, 970312,  1,   25,  0.084,  1.547,
 81, 970312,  1,   45,  0.098,  4.853,
 81, 970312,  1,   75,  0.173,  2.877,
 81, 970312,  1,  125,  0.127,  0.550,
 81, 970312,  1,  150,  0.054,  0.120,
 82, 970409,  1,    5,  0.064,  2.905,
etc

the idea is to integrate on column 4, but the only identifier for the range of values over which to integrate is the value in column 1. I can't seem to write a routine that says "while column 1 == some value, store columns 4, 5, and 6 in vectors, then integrate 5 and 6 over column 4, and then store the integrate values in an array. Then go onto the next column 1 identifier." Any help for this programming newbie would be appreciated. In the above, 79 is associated with 8 values to integrate, 80 with 7, and 81 with 6.

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Answer 1

Iman Ansari 2013-4-16

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https://ww2.mathworks.cn/matlabcentral/answers/72181-while-loop-question-number-2#answer_82366

编辑：Iman Ansari 2013-4-16

Hi

A=[ 79, 970108,  1,    5,  0.088,  6.383
 79, 970108,  1,   25,  0.075,  4.380
 79, 970108,  1,   45,  0.094,  0.710
 79, 970108,  1,   75,  0.221,  3.010
 79, 970108,  1,  100,  0.140,  0.793
 79, 970108,  1,  125,  0.094,  0.243
 79, 970108,  1,  150,  0.054,  0.117
 79, 970108,  1,  175,  0.022,  0.043
 80, 970218,  1,    5,  0.097,  6.293
 80, 970218,  1,   25,  0.096,  4.920
 80, 970218,  1,   45,  0.094,  2.533
 80, 970218,  1,   75,  0.125,  3.520
 80, 970218,  1,  100,  0.198,  2.257
 80, 970218,  1,  125,  0.222,  0.723
 80, 970218,  1,  175,  0.072,  0.107
 81, 970312,  1,    5,  0.091,  6.983
 81, 970312,  1,   25,  0.084,  1.547
 81, 970312,  1,   45,  0.098,  4.853
 81, 970312,  1,   75,  0.173,  2.877
 81, 970312,  1,  125,  0.127,  0.550
 81, 970312,  1,  150,  0.054,  0.120
 82, 970409,  1,    5,  0.064,  2.905];
C={};
for i=79:81
    C{i}=A(A(:,1)==i,logical([0 0 0 1 1 1]));
end
disp('C{79}=')
disp(C{79})
disp('C{80}=')
disp(C{80})
disp('C{81}=')
disp(C{81})

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Iman Ansari 2013-4-19

intval89 = zeros(10,3); % desired output
for i = 3:12 % identifier for sequence in C89
   N89 = C89{:,i};  % Why not use C89{i}
   intchl89 = trapz(N89(:,2),N89(:,3));
   intpp89 = trapz(N89(:,2),N89(:,4));
  %%%%%%%%%%%%%
   intval89(i,:) = [i intchl89 intpp89]; 
end

John 2013-4-19

Well that worked! Thanks for all the help. Now I can have a weekend!

Answer 2

Ahmed A. Selman 2013-4-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/72181-while-loop-question-number-2#answer_82410

In such a case, using a while loop cannot do the job, but an if statement can. So, I think this is what are you looking for (continued from the previous question/answer):

clear 
clc
% 1) Reading data from a text file. Change the name of the file first.
filename='johnText.txt'; % Change this filename
ID1=fopen(filename,'r');
[A b]=fscanf(ID1,'%g %*c',[1 inf]); % *c is to ignore the comma in the file
B=reshape(A,6,b/6); % 6 elements each line having numeric values w/no comma
B=B';
% 2) The math workout
[a2,b2]=size(B); % Now B=[Num X Y Z]
k=0;Acc=0;
CalCol=4; % Which column is to be used for sum or integration?
RefCol=1; % Which column is to be used as matching reference?
 DS(1:a2)=B(1:a2,CalCol);% first one only 
for i=1:a2 % on rows 
  j0=DS(i);
  if i==a2;break;end
   if ( B(i,RefCol)==B(i+1,RefCol) ) % if Num of B(1,j)=Num of B(1,j+1)
   Acc=Acc+B(i,CalCol);
   else
       k=k+1;
       A2(k)=Acc+B(i,CalCol); 
       Acc=0;
   end   
end 
disp('Your summation of col4 when col.1 is the same is: ');disp(' ');
disp(A2')

Please note that this is a code doing the summation over the 4th column whenever the first one is matched between successive rows. If you find it tricky to add another type of math instead of plane summation, do not hesitate to tell me about it.

Regards.

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John 2013-4-17

Thanks. Very helpful, I think.

I read in the data file using csvread('textfile.csv'), and instead of doing an accumulation, I just used the function trapz.

I think you're right that the 'if' statement is the way to go instead of 'while'. I'll have to educate myself on some of the other things, like size. Anyway, much appreciated.