MaplePrimes - answers and comments on Question, Correct upto 7 decimal figurs (not significant digits)

Reference

Markiyan Hirnyk — Sat, 12 Jan 2013 01:36:17 Z

A similar question was recently discussed here http://www.mapleprimes.com/questions/136468-Bug-Using-Evalf .

This link can be found by the "evalf" search in MaplePrimes at the top of this page.

something like this?

acer — Sat, 12 Jan 2013 02:22:24 Z

Are you looking for something like this, perhaps?

F:=x->parse(sprintf("%.7f",x)):

F(66666.123456789);
                                66666.1234568

F(0.123456789);
                                  0.1234568

F(0.12345);
                                  0.1234500

expr:=(lambda1-2.9881355172134833*lambda2
       +16.044692204509636*lambda1^2
       -114.31727386075951*lambda1*lambda2
       +202.36051939112247*lambda2^2):

subsindets(expr,float,F);
                                                           2
           lambda1 - 2.9881355 lambda2 + 16.0446922 lambda1 

                                                                 2
              - 114.3172739 lambda1 lambda2 + 202.3605194 lambda2

acer

interface(displayprecision=7):

PatrickT — Sat, 12 Jan 2013 06:28:38 Z

Depending on what the purpose is:

restart;
interface(displayprecision=7):
lambda1-2.9881355172134833*lambda2+16.044692204509636*lambda1^2-114.31727386075951*lambda1*lambda2+202.36051939112247*lambda2^2;

Precedent

Markiyan Hirnyk — Sat, 12 Jan 2013 03:08:06 Z

See the answer by Alec Mihailovs in http://www.mapleprimes.com/questions/43633-Round-To-A-Certain-Number-Of-Digits . This link can be found by the "digits" search in MaplePrimes at the top of this page.

if that is in fact the question

acer — Sat, 12 Jan 2013 05:22:18 Z

@Markiyan Hirnyk

Converting with parse(sprintf(..)) of a float format is one obvious way to treat individual floats (if this is in fact what the Asker wants).

The `subsindets` selection of all things of type `float` may work for this particular example where only the coefficients are to be changed. But it could be too heavy handed in other scenarios where some floats (eg, coefficients) were on target but other floats (eg. exponents) were not. Finer discrimination might be needed. But that too is pretty obvious.

One more precedent

Markiyan Hirnyk — Sat, 12 Jan 2013 12:05:57 Z

@acer See http://www.mapleprimes.com/questions/43784-Significant-Digits . This can be found by the "digits" search in MaplePrimes at the top of this page.