Re: extract elements from a list
- To: mathgroup at smc.vnet.net
- Subject: [mg2850] Re: extract elements from a list
- From: NEWSMGR at selu.edu
- Date: Wed, 27 Dec 1995 00:48:03 -0500
- Organization: Southeastern Louisiana University
>Subject: Re: extract elements from a list >From: koppel at omega.ee.lsu.edu (David M. Koppelman) >Organization: Louisiana State University ECE Dept. In article <4bg3ba$ob8 at dragonfly.wri.com> "cjkelly at bu.edu" <cjkelly at bu.edu> writes: > > I've been trying to extract elements from a list x={a,b,c,d,e...} > then square each value and pair it up with the original unsquared value. > These two values form a point (2Dim) and I then try to pair up each > point with a given vertex of {5,25} and use Line[{{5,25},{a,a^2}}] to > graph this thing. > > My main routine (reAlly kinda small) > is...Do[n=x[[i]];Line[{{5,25},{n,n^2}}],{i,10,1}] > > When this is run nothing happens.... > > in this case x={5,5.5,5.4,5.3,5.2...ect} There are several problems with the code above. First, a negative step should be used when iterating from 10 to 1. (Unless that was a typo.) The "Line" function doesn't draw a line when evaluated. Instead, "Line" is meaningful as an argument to "Graphics." Similarly, evaluating "Graphics" does not result in anything being drawn; it should be used as an argument to "Show" which will draw the stuff described by "Graphics." The following might do what you want: Show[Graphics[Line[{{5,25},{#,#^2}}]&/@{5,5.5,5.4,5.3,5.2}]] > I've been stuck for 2 weeks unable to get this to work and it is > driving me crazy because it should be sooo easy. One has not really experienced frustruation until one has worked with computers. __ /\ /\ /\ <> <> David M. Koppelman <> <> koppel at gate.ee.lsu.edu <> 102 EE Building <> <> (504)-388-5482 <> Louisiana State University <> <> http://www.ee.lsu.edu/koppel <> Baton Rouge, La 70803 <> ~~ ~~ ~~