Re: Vectorization and Numeric (Newbie)
"map" takes a function and a list, applies the function to each item in a list, and returns the result list. For example: >>> def f(x): return x + 4 >>> numbers = [4, 8, 15, 16, 23, 42] >>> map(f, numbers) [8, 12, 19, 20, 27, 46] So, rather that ask if there is a different way to write f, I'd just use f in a different way. Another way to accomplish the same result is with a list comprehension: >>> [f(x) for x in numbers] [8, 12, 19, 20, 27, 46] As you can see, if you wanted to "calculate all the values from 1 to n," you could also use these techniques instead of a loop. >>> n = 10 >>> [f(x) for x in xrange(1, n+1)] [5, 6, 7, 8, 9, 10, 11, 12, 13, 14] -- http://mail.python.org/mailman/listinfo/python-list
Re: Vectorization and Numeric (Newbie)
Ronny Mandal wrote: > Assume you have a mathematical function, e.g. f(x) = x + 4 > > To calculate all the values from 1 to n, a loop is one alternative. > Numeric and friends (numarray,numpy) have something like numarray.arange - they return arrays similar to the lists returned by standard libs range function. I would recommend using the built-in array operations as much as possible - in most cases they are much faster than looping, and your code remains simpler. > But to make this function work with vectors instead i.e > f(x_vector) = result_vector, > how should the function then be implemented? > In most numeric libraries, vectors and scalars can be added etc. For the simple f(x) case you can use just the simplest approach: def f(x): return x+4 and call this with scalar and vector args. f_pi = f(3.14159265) f_1to200 = f(numarray.arange(1,200)) -- http://mail.python.org/mailman/listinfo/python-list
Re: Vectorization and Numeric (Newbie)
Are you looking for the "map" function? >>> def f(x): return x+4 >>> map(f, [1,2,3,3,70]) [5, 6, 7, 7, 74] CyrilOn 2/28/06, Ronny Mandal <[EMAIL PROTECTED]> wrote: Assume you have a mathematical function, e.g. f(x) = x + 4To calculate all the values from 1 to n, a loop is one alternative.But to make this function work with vectors instead i.ef(x_vector) = result_vector, how should the function then be implemented?ThanksRM--Support bacteria - it's the only culture some people have!--http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Vectorization and Numeric (Newbie)
Assume you have a mathematical function, e.g. f(x) = x + 4 To calculate all the values from 1 to n, a loop is one alternative. But to make this function work with vectors instead i.e f(x_vector) = result_vector, how should the function then be implemented? Thanks RM -- Support bacteria - it's the only culture some people have! -- http://mail.python.org/mailman/listinfo/python-list
