significant digits in random numbers in scientificform
- To: mathgroup at smc.vnet.net
- Subject: [mg46278] significant digits in random numbers in scientificform
- From: sean_incali at yahoo.com (sean kim)
- Date: Fri, 13 Feb 2004 02:28:47 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
hello group. few more questions. how do I pick random numbers such that, when displayed in ScientificForm, the coefficients only vary to designated number of digits? Example: 1.2345x 10^1 has significant digits of 5 (1.2345), where as 1.2*10^3 has signficant digits of 2.(1.2) consider the following. In[601]:= rule1 = {k1 ->10^Random[Real,{1,3}, 2]//ScientificForm, k2 ->10^Random[Real,{1,3}, 5]//ScientificForm} k1 + k2/.rule1 but above gives following errors. ReplaceAll::reps :(k1 -> 1.4×10^2, k2 -> 7.875×10^1) is neither a list of replacement rules nor a valid dispatch table, and so cannot be used for replacing. "More?" What I wanted Mathematica to pick was something like... (random real number to given digits) *10^ (random integer chosen from range) So the question is two fold. How do I tell mathematica to pick random numbers only in designated number of digits? and use that in downstream calculations? if I use.. Random[Real, {1,10},5]* 10 ^ Random[Integer, {1, 3}] above does what I want but I hate the idea of using two Random, and I'm worried that it will cause problems. and i would liek to see how you guys would do it. will the routine be too slow If i have to use it many many times? and if so why and how do i fix it? thank you all very much in advance as always. sean