Bug in symbolic toolbox?
1 次查看(过去 30 天)
显示 更早的评论
Hi all, I am experiencing a strange behavior of the sym function. The result of sym('I') is 'I'. While the result of sym('A+I') is 'A+i' with an unwanted lower case letter of 'I'.
Has anyone experienced such a behavior? Is it a bug? and if so is there any workaround?
Thanks, Junior
0 个评论
采纳的回答
Walter Roberson
2011-8-18
In the input regions MuPAD recognizes an uppercase I as the imaginary unit (-1)^(1/2). In the output regions, MuPAD uses a lowercase i to display the imaginary unit
I – imaginary unit sqrt(-1) (see DOM_COMPLEX for details)
Complex numbers can be constructed by typing in the corresponding expression, such as 3+4*I. The keyword for typing the imaginary unit I is I (a capital letter i).
Thus, what you are seeing is not a bug.
I know that in Maple it is possible to change the representation letter, but I do not at the moment see any corresponding mechanism in MuPad. (In Maple, it would be by using interface(imaginaryunit=SYMBOL) )
更多回答(1 个)
Sean de Wolski
2011-8-18
It's seeing I as the sqrt(-1). What is your goal by doing it this way?
why not just
syms A I
A+I
?
The other easiest workaround would just be to use a different letter, J, or II.
sym('A+II')
5 个评论
Walter Roberson
2011-8-18
MuPad allows variable names that are not valid MATLAB variable names, so as long as you are processing at the MuPAD level, you could, for example, replace I by _I and strip off the underscore later.
Or.... http://www.mathworks.com/help/toolbox/mupad/datatypes/DOM_IDENT.html#DOM_IDENT
Additionally, an arbitrary string of characters enclosed in ‘backticks’ `` is also an identifier. Examples: `x+y`, `a plus 1`. If the string of characters between the back ticks is a valid identifier already, this input form creates the same identifier as the one without the backticks.
Thus, you could substitute (say) `I ` (with a space) where you have the variable I in your input, and the only visible difference with normal typesetting turned on would be an extra space after the I .
另请参阅
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!