Undefined function or variable in MATLAB

2013 7 19
3 个回答
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0 个投票

I have this function saved as element.m Whenever I call on it I say element(Hydrogen) I am trying to get it to display the name, symbol, atomic number, category, ... But it keeps saying Undefined function or variable 'Hydrogen' I don't understand why its doing this.
function [Name, Symbol, Atomic_Number, Category, Proton, Neutron, Electron]=element(e)
%Inputs:
%e - 'Hydrogen' ;
%Outputs:
%Name
%Symbol
%Atomic_Number
%Category
%Proton
%Neutron
%Electron
e=[Hydrogen Helium]
if e=='Hydrogen'
Name='Hydrogen';
Symbol='H';
Atomic_Number='1';
Category='Nonmetal';
Proton='1';
Neutron='';
Electron='1';
elseif e==Helium
Name='Helium'
Symbol='H'
Atomic_Number='1'
Category='Noble Gas'
Proton='4'
Neutron='2'
Electron='4'
end
end

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 采纳的回答

per isakson
per isakson 2013-7-19

0 个投票

What is e=[Hydrogen Helium] intended to do?

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Joshua
Joshua 2013-7-19
I meant to delete e=[Hydrogen Helium]
per isakson
per isakson 2013-7-19
???
At that point in the code neither Hydrogen nor Helium exists.
[A,B] concatenates the variables A and B
Joshua
Joshua 2013-7-19
how would i define hydrogen and helium if i wanted to get the name, category, symbol ...
per isakson
per isakson 2013-7-19
Remove the line
e=[Hydrogen Helium]
and replace
e=='Hydrogen'
by
strcmp( e, 'Hydrogen' )
or
all( e=='Hydrogen' )
Then try to run the function
Joshua
Joshua 2013-7-19
I did what you said with both strcmp and all, i tried both of them, when i wrote element('Hydrogen') in the command window it said ans=Hydrogen, but i dont understand why its not giving me the other information as well.
per isakson
per isakson 2013-7-19
You have to make a call like
[Name,Symbol,Atomic_Number,Category,Proton,Neutron,Electron]=element('Hydrogen')
Joshua
Joshua 2013-7-19
Thanks it worked.

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更多回答（2 个）

Azzi Abdelmalek
Azzi Abdelmalek 2013-7-19

0 个投票

The variable Hydrogene is not defined in your code, how Matlab will recognize it?

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Joshua
Joshua 2013-7-19
编辑：Joshua 2013-7-19
I am kind of new to MATLAB, how exactly would i define it if I wanted it to give me the Name, Category, Symbol ...
Joshua
Joshua 2013-7-19
Thanks it worked.

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Jason Schneider
Jason Schneider 2013-7-19

0 个投票

Remove
e = [Hydrogen Helium]
Use
strcmp as previously suggested.
Make sure when you call the function it is of the form:
[a b c d e f g] = element('Hydrogen')
You need to define where the rest of the output arguments will be assigned since they are internal variables to the function.
It seems this was also mentioned but the input argument needs to be a string or else Matlab will look for a variable that doesn't exist.

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