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From: Andy on 10 Aug 2010 11:35 Well, the error message is clear. Your expression is a symbolic expression, and it doesn't make sense to ask if one symbol is less than another. You need to convert your symbols to doubles before comparing them.
From: Kittithad Wangveerathananon on 10 Aug 2010 11:54 "Andy " <myfakeemailaddress(a)gmail.com> wrote in message <i3rrja$sr7$1(a)fred.mathworks.com>... > Well, the error message is clear. Your expression is a symbolic expression, and it doesn't make sense to ask if one symbol is less than another. You need to convert your symbols to doubles before comparing them. Wow, I never know about the function double before. Where does its name come from? I'm confues that it is all numbers, though still with operators included, but no symbols in the expression. Why it is regarded as a symbolic? Anyway, it works when applying double(), thanks for the tip. Your help is highly appreciated.
From: Steven_Lord on 10 Aug 2010 13:26
"Kittithad Wangveerathananon" <kittithad(a)startfromyou.com> wrote in message news:i3rsms$a7p$1(a)fred.mathworks.com... > "Andy " <myfakeemailaddress(a)gmail.com> wrote in message > <i3rrja$sr7$1(a)fred.mathworks.com>... >> Well, the error message is clear. Your expression is a symbolic >> expression, and it doesn't make sense to ask if one symbol is less than >> another. You need to convert your symbols to doubles before comparing >> them. > > Wow, I never know about the function double before. Where does its name > come from? I'm confues that it is all numbers, though still with operators > included, but no symbols in the expression. Why it is regarded as a > symbolic? Because that's what SOLVE returns. You can have a sym object that contains no symbolic variables at all, and that's perfectly valid. two = sym(2); This is useful for many reasons, one of which is computing large values without losing precision due to an intermediate result being stored in double. twoTo1500 = two^1500 twoTo1500Double = sym(2^1500) The former performs the calculation symbolically, while the latter performs the calculation numerically (which overflows to Inf) and converts that Inf result into a symbolic object. -- Steve Lord slord(a)mathworks.com comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ To contact Technical Support use the Contact Us link on http://www.mathworks.com |