[Tutor] numarray issues
Hello, I am a python beginner, and I have a question about scalars vs arrays. I am making a (very simple) code, and part of it is: from numarray import * from math import * def source(x,y): f=sin(x) return f a=4. m=10 dx=a/(m+1.) x=zeros([m,1], Float) print x[0] print func(x[0]) When I run this code, I get: [ 0.] 0.0 However, if I change the line f=sin(x) to f=2*x, I will get: [ 0.] [ 0.] Why does func(x[0]) return a scalar for sin(x), but returns an array for 2*x? If I want a scalar returned for f=2*x, I need to put in func(x[0,0]). Why do x[0] and x[0,0] both work for sin(x), but only x[0,0] will work for 2*x? ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] numarray issues
Mr Gerard Kelly wrote: Hello, I am a python beginner, and I have a question about scalars vs arrays. I am making a (very simple) code, and part of it is: from numarray import * from math import * def source(x,y): f=sin(x) return f a=4. m=10 dx=a/(m+1.) x=zeros([m,1], Float) print x[0] print func(x[0]) When I run this code, I get: [ 0.] 0.0 However, if I change the line f=sin(x) to f=2*x, I will get: [ 0.] [ 0.] Why does func(x[0]) return a scalar for sin(x), but returns an array for 2*x? If I want a scalar returned for f=2*x, I need to put in func(x[0,0]). Why do x[0] and x[0,0] both work for sin(x), but only x[0,0] will work for 2*x? sin() expects a scalar value. x[0] is a 1 element array. numarray magically converts the 1 element array to a scalar. x[0]*2 multiplies each element of the array by 2 giving an array result. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor -- Bob Gailer Chapel Hill NC 919-636-4239 ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] numarray issues
Please always reply-all so a copy goes to the list. Mr Gerard Kelly wrote: is there a quick way to convert a one element array into a scalar value so that I can use x[0] for all operations? x = x[0] - Original Message - From: bob gailer bgai...@gmail.com Date: Tuesday, December 16, 2008 11:19 am Subject: Re: [Tutor] numarray issues Mr Gerard Kelly wrote: Hello, I am a python beginner, and I have a question about scalars vs arrays. I am making a (very simple) code, and part of it is: from numarray import * from math import * def source(x,y): f=sin(x) return f a=4. m=10 dx=a/(m+1.) x=zeros([m,1], Float) print x[0] print func(x[0]) When I run this code, I get: [ 0.] 0.0 However, if I change the line f=sin(x) to f=2*x, I will get: [ 0.] [ 0.] Why does func(x[0]) return a scalar for sin(x), but returns an array for 2*x? If I want a scalar returned for f=2*x, I need to put in func(x[0,0]). Why do x[0] and x[0,0] both work for sin(x), but only x[0,0] will work for 2*x? sin() expects a scalar value. x[0] is a 1 element array. numarray magically converts the 1 element array to a scalar. x[0]*2 multiplies each element of the array by 2 giving an array result. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor -- Bob Gailer Chapel Hill NC 919-636-4239 -- Bob Gailer Chapel Hill NC 919-636-4239 ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
