Velocity Reviews > Perl > Math Functions in Perl

# Math Functions in Perl

coolchick
Guest
Posts: n/a

 11-05-2007
Hi All,

I am trying to compute few equations using perl.

This is the equation that I am trying to solve:

MI=171-5.2*ln(aveV)-0.23*aveV(g)-16.2*ln(aveLOC)
+50sin(sqrt(2.46*perCM))

I have all the variables: aveV, aveV(g), aveLOC and perCM.
So the equation is:

\$MI=171 - (5.2*(2.303*log(\$aveV)))-(0.23*\$ecc)-
(16.2*(2.303*log(\$aveLOC)))+(50*(sin(sqrt(2.46*\$pe rCM))));

where:
\$aveV= 239.530014548124
\$ecc=9
\$aveLOC=47
\$perCM=0.297872340425532

I am not getting the correct answer. I get MI=-2.56217048794884, which
is not correct.
I tried to break it down and the problem is that I don't think I have
the right libraries for math.
It is not computing sqrt, log, and sin correctly.

I am using:
use Math::Complex;
use Math::Trig;

Any help would be great!
Thanks,
naureen

Jürgen Exner
Guest
Posts: n/a

 11-05-2007
coolchick wrote:
> MI=171-5.2*ln(aveV)-0.23*aveV(g)-16.2*ln(aveLOC)
> +50sin(sqrt(2.46*perCM))
>
> I have all the variables: aveV, aveV(g), aveLOC and perCM.
> So the equation is:
>
> \$MI=171 - (5.2*(2.303*log(\$aveV)))-(0.23*\$ecc)-
> (16.2*(2.303*log(\$aveLOC)))+(50*(sin(sqrt(2.46*\$pe rCM))));
>
> where:
> \$aveV= 239.530014548124
> \$ecc=9
> \$aveLOC=47
> \$perCM=0.297872340425532
>
> I am not getting the correct answer. I get MI=-2.56217048794884, which
> is not correct.

This is a long shot, but is any of the iterim values exceedingly large or
small? If so then you fell victim to a variation of 'perldoc -q 999'.
The easiest remedy would be to rewrite the equation to avoid very
large/small iterim values. This is not trivial, but there is a reason why
Computer Numerics is a class of its own at university.

jue

smallpond
Guest
Posts: n/a

 11-05-2007
On Nov 5, 8:00 am, coolchick <(E-Mail Removed)> wrote:
> Hi All,
>
> I am trying to compute few equations using perl.
>
> This is the equation that I am trying to solve:
>
> MI=171-5.2*ln(aveV)-0.23*aveV(g)-16.2*ln(aveLOC)
> +50sin(sqrt(2.46*perCM))
>
> I have all the variables: aveV, aveV(g), aveLOC and perCM.
> So the equation is:
>
> \$MI=171 - (5.2*(2.303*log(\$aveV)))-(0.23*\$ecc)-
> (16.2*(2.303*log(\$aveLOC)))+(50*(sin(sqrt(2.46*\$pe rCM))));
>
> where:
> \$aveV= 239.530014548124
> \$ecc=9
> \$aveLOC=47
> \$perCM=0.297872340425532
>
> I am not getting the correct answer. I get MI=-2.56217048794884, which
> is not correct.
> I tried to break it down and the problem is that I don't think I have
> the right libraries for math.
> It is not computing sqrt, log, and sin correctly.
>
> I am using:
> use Math::Complex;
> use Math::Trig;
>
> Any help would be great!
> Thanks,
> naureen

Rearranging your equation to show intermediate terms:

\$aveV = 239.530014548124;
\$ecc = 9.0;
\$aveLOC = 47.0;
\$perCM = 0.297872340425532;

\$i1= (5.2 * (2.303*log(\$aveV)));
\$i2= (0.23 * \$ecc);
\$i3= (16.2 * (2.303*log(\$aveLOC)));
\$i4= (50 * (sin(sqrt(2.46*\$perCM))));

\$MI = 171.0 - \$i1 - \$i2 - \$i3 + \$i4;

print "171.0 - ",\$i1," - ",\$i2," - ",\$i3," + ",\$i4," = ",\$MI,"\n";

171.0 - 65.610465007406 - 2.07 - 143.64361681316 + 37.761911332617 =
-2.56217048794883

I don't think you have math errors. All of the terms are the
same order of magnitude. If the result is wrong, then it is
something in your formula. You do want log base e and angle
in radians, right?
--S

coolchick
Guest
Posts: n/a

 11-05-2007
Hi, thanks for the help but the problem is that I am trying to solve
the Coleman-Oman's model for computing a code Maintainability Index.
The equation has 'ln' which I equated to 2.303*log(). So how do I
compute that? If I do the same thing using a scientific calculator, I
get a different answer.
For the angle, shouldn't that be in degrees.

Here is the equation:
http://www.stsc.hill.af.mil/consulti...sw_measurement

coolchick
Guest
Posts: n/a

 11-05-2007
How did you get 'mi=115.830374853214 ' as your your answer?

How can I do this inside my perl code ?

J. Gleixner
Guest
Posts: n/a

 11-05-2007
coolchick wrote:
> How did you get 'mi=115.830374853214 ' as your your answer?
>
> How can I do this inside my perl code ?

At this point, most people would simply copy and paste the
relevant parts of the code into a file and experiment with
it on their own.

Michele Dondi
Guest
Posts: n/a

 11-05-2007
On Mon, 05 Nov 2007 05:00:35 -0800, coolchick
<(E-Mail Removed)> wrote:

>Hi All,
>
>I am trying to compute few equations using perl.

Perl is not oriented at solving equations. You can solve them
symbolically and throw in values to compute the value of some function
given the arguments to it.

Michele
--
{\$_=pack'B8'x25,unpack'A8'x32,\$a^=sub{pop^pop}->(map substr
((\$a||=join'',map--\$|x\$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,\$_,
256),7,249);s/[^\w,]/ /g;\$ \=/^J/?\$/:"\r";print,redo}#JAPH,

Michele Dondi
Guest
Posts: n/a

 11-05-2007
On Mon, 05 Nov 2007 10:03:18 -0800, Jim Gibson <(E-Mail Removed)>
wrote:

>> For the angle, shouldn't that be in degrees.

>
>perldoc -f log:
>
> log EXPR
> log Returns the natural logarithm (base e) of EXPR.

For some reason, pocket calcultators have this habit of calling log_10
log and log_e ln. In my mathematical writings I just stick with log to
mean "their" ln. logarithms in any other base (unless explicitly
shown) are of little mathematical relevance, IMHO.

Michele
--
{\$_=pack'B8'x25,unpack'A8'x32,\$a^=sub{pop^pop}->(map substr
((\$a||=join'',map--\$|x\$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,\$_,
256),7,249);s/[^\w,]/ /g;\$ \=/^J/?\$/:"\r";print,redo}#JAPH,

Martijn Lievaart
Guest
Posts: n/a

 11-05-2007
On Mon, 05 Nov 2007 21:49:38 +0100, Michele Dondi wrote:

> For some reason, pocket calcultators have this habit of calling log_10
> log and log_e ln. In my mathematical writings I just stick with log to
> mean "their" ln. logarithms in any other base (unless explicitly shown)
> are of little mathematical relevance, IMHO.

I use log2 on a nearly daily basis. But then, I'm in computers while I
could have learned a trade.

M4

Michele Dondi
Guest
Posts: n/a

 11-05-2007
On Mon, 5 Nov 2007 23:42:03 +0100, Martijn Lievaart
<(E-Mail Removed)> wrote:

>> For some reason, pocket calcultators have this habit of calling log_10
>> log and log_e ln. In my mathematical writings I just stick with log to
>> mean "their" ln. logarithms in any other base (unless explicitly shown)
>> are of little mathematical relevance, IMHO.

>
>I use log2 on a nearly daily basis. But then, I'm in computers while I
>could have learned a trade.

Hehe, in fact I was about to say that, probably along the lines of "a
second, but distant competitor being log_2". In fact information
theory is a respectable mathematical one also in its own respect i.e.
abstractly and regardless of any physical computer...

Michele
--
{\$_=pack'B8'x25,unpack'A8'x32,\$a^=sub{pop^pop}->(map substr
((\$a||=join'',map--\$|x\$_,(unpack'w',unpack'u','G^<R<Y]*YB='
..'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,\$_,
256),7,249);s/[^\w,]/ /g;\$ \=/^J/?\$/:"\r";print,redo}#JAPH,

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