Eval with multiple lines

I have to run following with eval function in a single line.

 a = 1:20; % first step is to define a variable 
 b = '[nan a(2:end)]'; % then index should be used. This should be in a single line.
 c = eval(b);

My proposal is (which is wrong);

 >> b = 'a = 1:20; [nan a(2:end)]'; % I need a single line such this
 >> c = eval(b)
 Error: The expression to the left of the equals sign is not a
 valid target for an assignment.

There are some suggestions not to use eval. I have to use. Any help apreciated!

Answer 1

[Walter Roberson]

You cannot return a value from eval().

Does the assignment specifically require you to use eval()? We firmly discourage the use of eval().

http://uk.mathworks.com/matlabcentral/answers/251329-can-i-execute-matlab-script-that-is-written-in-edit-box-in-a-gui-created-by-guide#answer_197570

[Mehmet OZC]

I think I have to use it. Walter, will following code always work?

 eval(b);
 c = ans;

[Walter Roberson]

I do not know if it will always work; it might work.

Could you post a copy of the assignment text?

[Mehmet OZC]

 >> b = 'a = 1:20; [nan a(2:end)]'; % I need a single line such this
 >> eval(b)
 >> c = ans;

[Walter Roberson]

Right. Please post the text of the assignment.