grouping variables
in [Matlab]
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From: Dave400 on 13 Aug 2010 13:45 So, I have a problem that i hope a regular user can help me with. I have 1400 variables in my workspace named ‘a_1, a_2, a_3’ and so on. I would like to be able to group these into a single variable named ‘a_total’ which includes the 1400 single values, i.e a_total = <1x1400 double>. I have tried using a for loop but pretty sure I am missing something as I get an error message ??? Undefined function or method 'a_' for input arguments of type 'double'. j=1; for j = 1:1400 a_total = a_(j); end any help resolving this issue would be very much appreciated as a manual process would take ages. Regards, DR
From: Andy on 13 Aug 2010 13:55 "Dave400 " <dave.rogers(a)hotmail.co.uk> wrote in message <i440bh$j3q$1(a)fred.mathworks.com>... > So, I have a problem that i hope a regular user can help me with. > > I have 1400 variables in my workspace named ‘a_1, a_2, a_3’ and so on. > > I would like to be able to group these into a single variable named ‘a_total’ which includes the 1400 single values, i.e a_total = <1x1400 double>. > > I have tried using a for loop but pretty sure I am missing something as I get an error message > > ??? Undefined function or method 'a_' for input arguments of type 'double'. > > j=1; > for j = 1:1400 > a_total = a_(j); > end > > any help resolving this issue would be very much appreciated as a manual process would take ages. > > Regards, > > DR A few questions: 1) Are the a_n the only variables in the workspace? 2) Why did you create them all in the first place? Why not start with a_total? 3) Have you read the FAQ, specifically question 4.6: http://matlabwiki.mathworks.com/MATLAB_FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F
From: Matt J on 13 Aug 2010 14:08 "Dave400 " <dave.rogers(a)hotmail.co.uk> wrote in message <i440bh$j3q$1(a)fred.mathworks.com>... > So, I have a problem that i hope a regular user can help me with. > > I have 1400 variables in my workspace named ‘a_1, a_2, a_3’ and so on. As Andy said, the fact that you are in this situation is suspicious. However, this should do the concatenation for you a_total = [arrayfun(@(x)evalin('caller', ['a_' num2str(x)]),1:1400)];
From: Dave400 on 13 Aug 2010 14:20 "Matt J " <mattjacREMOVE(a)THISieee.spam> wrote in message <i441m4$f73$1(a)fred.mathworks.com>... > "Dave400 " <dave.rogers(a)hotmail.co.uk> wrote in message <i440bh$j3q$1(a)fred.mathworks.com>... > > So, I have a problem that i hope a regular user can help me with. > > > > I have 1400 variables in my workspace named ‘a_1, a_2, a_3’ and so on. > > As Andy said, the fact that you are in this situation is suspicious. However, this should do the concatenation for you > > a_total = [arrayfun(@(x)evalin('caller', ['a_' num2str(x)]),1:1400)]; thank you both. Matt, that works great out of interest i have attached my message before you sen yours, so any tips on this would be good also I am generating 7000 values and want to conduct a convergence study on the impact of the number of samples used. So I wanted to grab the first 5 then the next and so on until I had 1400 variables each with 5 values present. I didn’t know how to group them in the loop so though it was best to do a separate loop on the variables to avoid confusion. My original code is below M = <1x7000 double> b = 5; c = 1; a = zeros(1400,5); for k = 1:1400 a(k,:) = M(idx(1,c:b)); b = b+5; c = c+5; d(k,:) = mean(a(k,:)); name='a_'; vn=sprintf('%s%1.1d',name,k); eval([vn '(:,:) = [d(k,:)]; ']) end this generated variables a_1, a_2 a_3 and so on. When I tried adding the extra stage in the final value was the only one that remained instead of incrementing each on in a single variable name.
From: Matt J on 13 Aug 2010 14:41 "Dave400 " <dave.rogers(a)hotmail.co.uk> wrote in message <i442d5$114$1(a)fred.mathworks.com>... > b = 5; > c = 1; > a = zeros(1400,5); > for k = 1:1400 > a(k,:) = M(idx(1,c:b)); > b = b+5; > c = c+5; > d(k,:) = mean(a(k,:)); > name='a_'; > vn=sprintf('%s%1.1d',name,k); > eval([vn '(:,:) = [d(k,:)]; ']) > end ======== You could have just done a= reshape( M(idx(1,:)), 5,[]) ).'; d=mean(a,2); a_total=d;
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