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Selecting particular data range from matrix

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Mark Twen
Mark Twen on 12 May 2015
Edited: Michael Haderlein on 12 May 2015
Hello.I have got problem while selecting particular data range from my wind data,which includes approximately 884000 rows and 7 columns(1st column=station number,2nd column = year,3rd column= month,4th column=day,5th column = hour,6th column = speed,7th column = direction).I am trying to select speed according to particular station=>year=>month=>day=>hour.I wrote own code,but i think i do something wrong.Can anybody help me to solve this?I put piece of data and own code in order to show how my data is looks like.
fileID=fopen('wind.txt'); data=textscan(fileID,'%d %d %d %d %d %d %s'); fclose(fileID); Station=input('Enter station number = '); Year=input('Enter year = '); Month=input('Enter month = '); Day=input('Enter day = '); Hour=input('Enter hour = '); S=[]; Y=[]; M=[]; D=[]; H=[]; Spd=[]; Dir=[];
(data{1,1}==Station) & (data{1,2}==Year) & (data{1,3}==Month) & (data{1,4}==Day) & (data{1,5}==Hour); S=find(data{1,1}==Station); Y=find(data{1,2}==Year); M=find(data{1,3}==Month); D=find(data{1,4}==Day); H=find(data{1,5}==Hour); Spd=data{1,6}(H); Dir=data{1,7}(H);
%Average speed
Average_speed = mean(Spd)
%Produced power r=60; A=360; v=Average_speed; Produced_power = 0.5*r*A*v.^3
%

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Answers (1)

Michael Haderlein
Michael Haderlein on 12 May 2015
No data is available and the code is not formatted. Please use the {}Code button for proper code formatting and please not only select your data but also upload it.
I guess you can simplify your code by using textscan(fileID, format, 'collectoutput', 'true' ). Then you can easily access the "identifier" of your data (e.g. [1 2015 5 12 8]) as member of the submatrix data(:,1:5). Use ismember() for this.

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Mark Twen
Mark Twen on 12 May 2015
Excuse me, i did not understand you.My matlab knowledges are not so good. I have searched some informations about ismember(),and none of them matches with mine.In my project i want to take particular range of data,and the ranges of data will be specified by me.For example: i want to know the average speed of wind which corresponds to station number 17840,year 1994,month 5,day 5,hour 6.How can i do that.Can you look into my code,what exactly i do wrong?Can you give similar examples to do that.
Michael Haderlein
Michael Haderlein on 12 May 2015
You access your data with
datac=textscan(fileID,format,'collectoutput',true);
data=datac{1};
Maybe your data looks like this.
1 2015 3 14 8 4.12 91.54
1 2015 3 14 9 4.27 88.31
1 2015 3 14 10 6.37 90.47
1 2015 3 14 11 5.16 91.46
2 2015 3 14 8 8.12 12.42
2 2015 3 14 9 3.27 65.19
2 2015 3 14 10 2.37 50.77
2 2015 3 14 11 1.16 35.63
1 2015 3 15 8 1.37 13.78
1 2015 3 15 9 1.41 64.13
1 2015 3 15 10 0.89 16.54
1 2015 3 15 11 1.01 34.45
2 2015 3 15 8 0.37 53.86
2 2015 3 15 9 0.41 84.38
2 2015 3 15 10 1.89 56.45
2 2015 3 15 11 0.01 43.52
So you have two stations, data from 14th and 15th of March this year and only for 8-11 am. If I got you right, you want for instance the speed and direction for the second station at March 14th at 9 am, right? Then, your search pattern is
inp=[2 2015 3 14 9];
and you find the corresponding values with
[~,ind]=ismember(data(:,1:5),inp,'rows');
data(ind==1,6:7)
ans =
3.2700 65.1900
Which is speed/velocity at said station/time.

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