Calculating with tolerances

That won't do much good. ?Tolerances don't add (except in rare
circumstances), and certainly not when they're in different units.

There's nothing wrong with the first part, i.e. setting up variables whose
contents include the mean and the tolerance, but is that peak? or sigma?
?and so on.

Then you need to apply the errors properly. ?If the variables are
uncorrelated, there are some simple formulas for calculating the variance of
a product based on the magnitudes of the items and on their variances.
?Stuff all that into some function

product.tolerance<- function(q,h){
? ? ? ?productmean = 5*q[1]*h[1]
? ? ? ?productvariance = 5*q[1]^2*h[2] + 5*h[1]^2*q[2] + q[2]*h[2]*5
? ? ? ?return(list(productmean,productvariance)
? ? ? ?}
That's not exactly correct, but you see how this goes.

Carl

<quote>
From: Bernardo Rangel Tura <tura_at_centroin.com.br>
Date: Thu, 09 Sep 2010 05:58:35 -0300

On Thu, 2010-09-09 at 09:16 +0430, Jan private wrote:

Dear list,

I am from an engineering background, accustomed to work with tolerances.

For example, I have measured

Q = 0.15 +- 0.01 m^3/s
H = 10 +- 0.1 m

and now I want to calculate

P = 5 * Q * H

and get a value with a tolerance +-

What is the elegant way of doing this in R?

Thank you,
Jan

Hi Jan,

If I understood your problem this script solve your problem:

q<-0.15 + c(-.1,0,.1)
h<-10 + c(-.1,0,.1)
5*q*h
[1] 2.475 7.500 12.625
</quote>

I tried RSiteSearch("Interval aritmetic")
which gives zero hits.

There exist a   http://www.boost.org/
free software library for interval aritmetic, which it shoub be
possible to link to R.

Kjetil

On Thu, Sep 9, 2010 at 6:28 PM, Carl Witthoft <carl at witthoft.com> wrote:

That won't do much good. ?Tolerances don't add (except in rare
circumstances), and certainly not when they're in different units.

There's nothing wrong with the first part, i.e. setting up variables whose
contents include the mean and the tolerance, but is that peak? or sigma?
?and so on.

Then you need to apply the errors properly. ?If the variables are
uncorrelated, there are some simple formulas for calculating the variance of
a product based on the magnitudes of the items and on their variances.
?Stuff all that into some function

product.tolerance<- function(q,h){
? ? ? ?productmean = 5*q[1]*h[1]
? ? ? ?productvariance = 5*q[1]^2*h[2] + 5*h[1]^2*q[2] + q[2]*h[2]*5
? ? ? ?return(list(productmean,productvariance)
? ? ? ?}
That's not exactly correct, but you see how this goes.

Carl

<quote>
From: Bernardo Rangel Tura <tura_at_centroin.com.br>
Date: Thu, 09 Sep 2010 05:58:35 -0300

On Thu, 2010-09-09 at 09:16 +0430, Jan private wrote:

Dear list,

I am from an engineering background, accustomed to work with tolerances.

For example, I have measured

Q = 0.15 +- 0.01 m^3/s
H = 10 +- 0.1 m

and now I want to calculate

P = 5 * Q * H

and get a value with a tolerance +-

What is the elegant way of doing this in R?

Thank you,
Jan

Hi Jan,

If I understood your problem this script solve your problem:

q<-0.15 + c(-.1,0,.1)
h<-10 + c(-.1,0,.1)
5*q*h
[1] 2.475 7.500 12.625
</quote>