Attempt to extract field 'iterations' from 'mxArray'

2018 10 26
2 个回答
回答已采纳
更新时间：2018 11 11
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Hello! I need help. My problem is in Title. I use codegen for translate .m-code in mex.
[xopt,zmin,exitflag,output,lambda] = linprog(C1,A,B,[],[],LB1,[],[],options);
fprintf(1,Out1,xopt,zmin);
fprintf(1,'ExitFlag= %d\nIterats= %d\n',exitflag,output.iterations);
How can I solve this problem?

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Grek Vardugin
Grek Vardugin 2018-11-11

0 个投票

I solve it. First, I created a new structure with fields that exist in the output structure.
output = struct('iterations', 0, 'constrviolation', 0, 'message', '', 'algorithm', '', 'firstorderopt', 0);
Then I added the coder.varsize function for text fields.
coder.varsize('output.message', [1,100]);
coder.varsize('output.algorithm', [1,100]);
After
[xopt,zmin,exitflag,output,lambda] = linprog(C,A,B,Aeq,Beq,lb,ub,[],options);
fprintf(1,Out1,xopt,zmin);
fprintf(1,'\nExitFlag = %d\nIterats = %d\n',exitflag,num2str(output.iterations));

更多回答（1 个）

Joh Hag
Joh Hag 2018-10-26

0 个投票

hi, is output a struct? the mxArray is just the bare data and does not have such a field. have you tried to put the value in a separate variable such num_iterations = output.iterations? and then use this one in the fprintf command. this could help codegen to sort things out.

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Grek Vardugin
Grek Vardugin 2018-10-26
Hi, Jon! Thank you for your answer! Yes, output is a struct, where output.iterations is integer type. My goal is to execute the linprog function and write some of its results to a file. In this case, write output.iterations.
Joh Hag
Joh Hag 2018-10-26
Did you try the trick with the temporary variable? where does the compilation actually fail? at the fprintf's or when you call linprog?
Grek Vardugin
Grek Vardugin 2018-10-26
Compilation failed then I use fprintf. If I use the disp function instead of fprintf, I get a similar error.

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