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How to generate names?

Asked by Hello kity on 8 Jan 2013

I want to make my code shorter.

I have this code:

Sheetname1=txt1{1,3};
Sheetname2=txt2{1,3};
Sheetname3=txt3{1,3};
Sheetname4=txt4{1,3};
Sheetname5=txt5{1,3};
Sheetname6=txt6{1,3};

instead there should be a for loop

for i=1:6
 Sheetname'write i'=txt'write i'{1,3};
end

how to :) ?

1 Comment

Hassan F on 8 Jan 2013

Is there a specific reason why you implemented your script this way? Such a for loop will be slow and hard to read later on.

Hello kity

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5 Answers

Answer by Hassan F on 8 Jan 2013

You can use eval

for i=1:6
 eval(['Sheetname' num2str(i) '=txt' num2str(i) '{1,3};'])
end

5 Comments

Matt J on 8 Jan 2013

No, it's still not advised because

  • You're introducing variables non-explicitly into the workspace (so-called poofing). This creates hazards discussed here.
  • Enumerating variables through their names makes them hard to index later

The better thing to do here would be

    for i=1:6
     Sheetname{i} = eval(['txt' num2str(i) '{1,3};'])
    end
Jan Simon on 8 Jan 2013

I do think that it matters. Programmers get used to use methods they are used to use. The more EVAL you write, the more acceptable does this command look, because we are human.

Much better in theory, practice and from the viewpoint of training the brain to think in efficient ways:

Sheetname{1} = txt{1,3};
Sheetname{2} = txt{2,3};
Sheetname{3} = txt{3,3};
Sheetname{4} = txt{4,3};
Sheetname{5} = txt{5,3};
Sheetname{6} = txt{6,3};

Never include an index in the name of a variable. You would not include your current weight to your name also, because the inconveniences are obviously.

Kind regards, Jan70.6kg

Hassan F on 8 Jan 2013

Totally makes sense.

Hassan74.0kg

Hassan F
Answer by Hello kity on 8 Jan 2013

I tried this : >>

for i=1:6
A=['Sheetname' sprintf('%d' , i)];
B=['txt' sprintf('%d', i)];
A(i)=B{1,3}(i);
 end
??? Cell contents reference from a non-cell array object.

somehow it gives error about B{1,3}

while

>> txt1{1,3}

ans =

T1

1 Comment

Hassan F on 8 Jan 2013

See my answer http://www.mathworks.se/matlabcentral/answers/58253#answer_70475, but you should avoid this solution and use cells or other classes which suits your data the most.

Hello kity
Answer by Azzi Abdelmalek on 8 Jan 2013
A=cell(1,6);
for ii=1:6
A{ii}=sprintf('Sheetname%d' , ii)
end 

0 Comments

Azzi Abdelmalek
Answer by Image Analyst on 8 Jan 2013

My m-files are usually 2-3 thousand lines long. I never worry about saving a paltry 3 lines. Why do you care? If you want to use fewer variables, say use a cell array for Sheetname instead of 6 variables, then you could do that, but with only 6 variable, it's really no big deal. Now if you had dozens or hundred variables named like that (which we see sometimes).....then yes, you'd want an array, but I'm not going to ding you for only 6 uniquely named variables.

0 Comments

Image Analyst

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