HP PRIME: derivative at a point  Printable Version + HP Forums (https://archived.hpcalc.org/museumforum) + Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum1.html) + Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum2.html) + Thread: HP PRIME: derivative at a point (/thread256304.html) 
HP PRIME: derivative at a point  Alasdair McAndrew  11182013 I was experimenting with some interpolation techniques; in the CAS view of the Functions app I've entered:
{3,1,2,5} > xs So far so good. Now what I want to do is evaluate the derivative of q(x) at all the elements of xs. Here's where I get stuck: "diff" only computes symbolic derivatives, and SLOPE doesn't seem to work:
SLOPE(q(x),7) return 0 and "Error: Undefined Result" respectively.
q(x) returns (3+x)*(1+x)*(2+x)*(5+x) as it should In Home view,
q(x) returns Error: Syntax Error So no joy there. I have discovered that, for example
eval(diff(q(x)),x=3) will, for example, compute the derivative at a point. But it won't let me pick out a list element:
eval(diff(q(x)),x=xs(1)) produces a long expression full of "xs(1)": clearly for some reason this is not treated as a numeric value. The best I can do is
seq(eval(diff(q(x)),x=k),k=xs) > ds which works, but is confusing. (MAKELIST doesn't seem to work here: in fact MAKELIST hardly even seems to work). Are there any "natural" ways to perform these sort of computations?
[Note, on both the TInspire and the Casio ClassPad I would just use "diff(q(x)(x=xs)".] Edited: 18 Nov 2013, 10:39 p.m.
Re: HP PRIME: derivative at a point  Tim Wessman  11182013 dq(x)/dx=xs or (dq(x)/dx)x=xs both work I beleive. X exists because it is a nonremovable home real variable. Also, there is not any such thing as a <application> HOME or <applicaiton> CAS view. There is 1 CAS view, and 1 home view. The application is "active" while you are in those views, but it is not attached to it in any way.
Re: HP PRIME: derivative at a point  parisse  11192013 map(xs,q') or apply(q',xs) Edited: 19 Nov 2013, 6:58 a.m.
