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Substitution problem in matlab

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Michael Elman
Michael Elman 2018-9-13
评论： madhan ravi 2018-9-13
Hello, I'm new in matlab, and I'm trying to learn operations with variables,so I have encountered a little problem, that I don't quite understand, why
ER=subs(yp,{sx},{1})
ER=subs(yp,{sy},{1})
it's not a same thing, as
ER=subs(yp,{sx,sy},{1,1})
? In first case the answer is
-y*(exp(-x^2/sx^2)*exp(-y^2) - 1)
(and I don't want sx^2) and in the second case the answer is
-y*(exp(-x^2)*exp(-y^2) - 1)
(this is exactly, what i need)
This is my starting code:
syms x y z;
syms sx sy;
yp=y*(1-exp(-x^2/sx^2)*exp(-y^2/sy^2))
Does someone know what's the reason behind it?
  1 个评论
madhan ravi
madhan ravi 2018-9-13
编辑：madhan ravi 2018-9-13
Can you format the code by selecting the whole code and clicking the code button?

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madhan ravi
madhan ravi 2018-9-13
编辑：madhan ravi 2018-9-13
syms x y z;
syms sx sy;
yp=y*(1-exp(-x^2/sx^2)*exp(-y^2/sy^2))
ER=subs(yp,{sx},{1})
ER=subs(ER,{sy},{1})
ER1=subs(yp,{sx,sy},{1,1})
Reason: when you wanted to substitute for sy the second time you should type ER instead of up because you’re replacing the old equation again
TYPE:
ER=subs(ER,{sy},{1})
INSTEAD OF:
ER=subs(yp,{sy},{1})

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