## Search found 67 matches

Sat Feb 09, 2008 6:23 am
Forum: Mathematics
Topic: Half of a mortgage nomogram
Replies: 9
Views: 32386
The sort of "automatic identification of smooth transformations" we've just been discussing is a problem I have been worrying at for a long time, but I always failed to figure out how to automatically identify the transformation of the response variable from a fairly general smooth class (...
Fri Feb 08, 2008 9:23 pm
Forum: Mathematics
Topic: Half of a mortgage nomogram
Replies: 9
Views: 32386
How about if you would just fit coeffs for polynomials F1,F2,G2,F3 in function F1(a)=F2(n)+G2(n)*F3(i) such that error would be minimized for every combination of a,n,i in specified range ? This is of course the approach I already proposed. Indeed you could attempt to fit smooth curves. In many cas...
Fri Feb 08, 2008 5:58 am
Forum: General
Topic: Spam, etc.
Replies: 9
Views: 68815
Those last two look a bit suspicious to me. Are they legit?
Fri Feb 08, 2008 2:42 am
Forum: Mathematics
Topic: Half of a mortgage nomogram
Replies: 9
Views: 32386

### Re: Half of a mortgage nomogram

[quote="RonDoerfler"][quote="Glenbarnett"]I have made the right half of this equation into a nomogram (i.e. the tricky part), following largely the "one curvy scale" discussion I posted here recently. [/quote] I understand why you might expect the a and i scales to be l...
Thu Feb 07, 2008 7:44 am
Forum: General
Topic: Spam, etc.
Replies: 9
Views: 68815
Well done. Seem like we might have another one. Maybe they got in before you changed the setup.
Thu Feb 07, 2008 6:05 am
Forum: Mathematics
Topic: Half of a mortgage nomogram
Replies: 9
Views: 32386

### Half of a mortgage nomogram

The mortgage nomogram Leif was describing has two main parts. If P is the loan amount (P stands for Principal), m is the monthly payment, i is the monthly interest rate, and n is the term in months then P/m = a = [1-(1+i)^{-n}]/i Of course, the user wants the interest quoted as an annual rate and th...
Wed Feb 06, 2008 8:07 am
Forum: Mathematics
Topic: Shared scales
Replies: 1
Views: 13798

### Anamorphosis with back to back scales

The usual double-anamorphosis (due to Lafay) that is in the books is generally better than the simpler single anamorphosis - which can still be useful when all of the curves on the intersection chart are similarly curved. However, there is a situation in which adjusting a single scale is more useful...
Tue Feb 05, 2008 3:35 am
Forum: General
Topic: Spam, etc.
Replies: 9
Views: 68815
While we're at it, there seems to be a dozen spammer accounts here already.

It's probably worth deleting them before they post more spam.

At the least, can you set the signup to require the intervention of an admin?
Tue Feb 05, 2008 1:48 am
Forum: Literature
Topic: A recommended paper
Replies: 0
Views: 18900

### A recommended paper

I was going through some of my old nomography stuff, and came across this one again - I've been looking for it lately, and I'm glad I found it, because it was better than I remembered. If you have access to it, I highly recommend Philip Lyle's paper (note only one L in the first name!): Philip Lyle ...
Mon Feb 04, 2008 1:21 am
Forum: General
Topic: Spam, etc.
Replies: 9
Views: 68815
Is it possible to do one of the following two: (i) have a CAPTCHA or something on signup, so bots cant sign themselves up? An easy one would be to answer a simple question about nomograms or something. There could always be an alternative route via email or something where you just explain why you n...
Sun Feb 03, 2008 8:39 pm
Forum: Mathematics
Topic: Two straight scales with a weird curvy scale in the middle
Replies: 9
Views: 37000
[quote="Leif"]For interest, I think it was 1% to 10% and 5 to 50 years. By polynomials I got somewhere of 4% maximum error if I recall right. It was anyway little too much. For transformations: transformations do not change the basic equation. But maybe transformation could be such that in...
Sun Feb 03, 2008 4:03 am
Forum: Mathematics
Topic: Two straight scales with a weird curvy scale in the middle
Replies: 9
Views: 37000
What range of terms and interest rates were you looking at?
Sat Feb 02, 2008 10:41 pm
Forum: Mathematics
Topic: Two straight scales with a weird curvy scale in the middle
Replies: 9
Views: 37000
[quote="Leif"]My feeling is, that by taking the most general three variable nomogram of form g(u){ f(v) - f(w) } + g(v){ f(w) - f(u) } + g(w){ f(u) - f(v) } = 0 [see. e.g. http://www.projectrho.com/nomogram/standardForms.html] and fit polynomials to all six functions to match the real equa...
Sat Feb 02, 2008 5:05 am
Forum: Mathematics
Topic: Two straight scales with a weird curvy scale in the middle
Replies: 9
Views: 37000
It occurs to me that it seems possible to do this sort of anamorphic/rectification calculation automatically.

I might see if I can get some time in a couple of weeks and write an algorithm.
Fri Feb 01, 2008 6:43 am
Forum: Mathematics
Topic: Two straight scales with a weird curvy scale in the middle
Replies: 9
Views: 37000
[quote="Leif"]If I understand correctly, this is close to a term "rectification of curves" that is discussed e.g. in Ref. [p. 180, Levens, 2nd Ed, 1965]. The question is how one can make log(f(x))-log(g(y)) plots where all curves g(z)=const are straight lines. Sometimes this does...