use of eval

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Tor Fredrik Hove
Tor Fredrik Hove el 21 de Oct. de 2011
I am trying to use evalfunction but are having a hard time:
>> plots=[3 4 6 1]
plots =
3 4 6 1
>> whatplot=input('type type of graph: ','s')
type type of graph: bar
whatplot =
bar
>> eval(whatplot(plots))
??? Index exceeds matrix dimensions.
>>
why wont it evaluate it to a graph with bars?

Respuesta aceptada

Wayne King
Wayne King el 21 de Oct. de 2011
Your call to input() returns the string bar in whatplot
but whatplot(plots) is not a string.
eval([whatplot '(plots)'])
  4 comentarios
Tor Fredrik Hove
Tor Fredrik Hove el 21 de Oct. de 2011
thanks! I guess I am also a bit confussed about my book. It says:
>>x=[9 7 10 9];
whatplot=input('What type of plot?: ','s');
What type of plot?: bar
>>eval([whatplot '(x)'])
>>title(whatplot)
>>xlabel('Student#')
>>ylabel('Quiz Grade')
I guess the three last lines are just for naming graph and coordinates but thoose before don't return any graph for me
Jan
Jan el 22 de Oct. de 2011
Bad book. Evil EVAL.

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Más respuestas (2)

Patrick Kalita
Patrick Kalita el 21 de Oct. de 2011
I think feval would be a better option here. It is a safer than eval, and it easily accommodates passing input arguments:
feval( whatplot, plots )
  3 comentarios
Jan
Jan el 21 de Oct. de 2011
@Tor: Avoid EVAL. As you see, it causes troubles.
Tor Fredrik Hove
Tor Fredrik Hove el 21 de Oct. de 2011
it is part of curriculum unfortunately:) If not I would have:)

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Wayne King
Wayne King el 21 de Oct. de 2011
plots=[3 4 6 1];
whatplot = 'bar';
eval([whatplot '(plots)'])
  1 comentario
Wayne King
Wayne King el 21 de Oct. de 2011
also, see the comments by other posters above.

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