Calculating Standard Deviation

I needed to do this for one of my hobby sites, so I thought I would share. Good if you have a scoring or ratings system on your site.

make sure that you have a tab on this line as indicated:
sdev[index]<tab>[math][interpret][dev[index]][/interpret]*[interpret][dev[index]][/interpret][/math]



[!]<!-- The following code will find the standard deviation-->[/!]
[!]<!-- in a range of numbers stored in a database (or table), -->[/!]
[!]<!-- where math.db is your database of scores -->[/!]
[!]<!--
SAMPLE DATABASE:
rating
8
5
6
5
4
9
7
1
5
6
-->[/!]
[!]<!--Should yield a STANDARD DEVIATION of 2.22-->[/!]

[search db=math.db&neRATINGdatarq=[blank]]
[text show=F]numscores=[numfound][/text]
[founditems]
Rating [index]=[text show=T]num[index]=[rating][/text]<br>
[/founditems]
Total: [text show=T]total=[sum field=rating][/text]<br>
[/search]
Avg: [text show=T]avg=[math][total]/[numscores][/math][/text]<br>
<hr>
[loop start=1&end=[numscores]]
[text show=f]dev[index]=[math]([interpret][num[index]][/Interpret]-[avg])*-1[/math][/text]
[/loop]
[table name=sdev&fields=sku,sdevnum]
[loop start=1&end=[numscores]]
sdev[index]<tab>[math][interpret][dev[index]][/interpret]*[interpret][dev[index]][/interpret][/math]
[/loop]
[/table]
[search table=sdev&neskudatarq=[blank]]
[text show=f]devsum=[sum field=sdevnum][/text]<br>
[/search]

[text show=f]ass=[math][devsum]/([numscores]-1)[/math][/text]
Standard Deviation =[format .2f][math]sqrt([ass])[/math][/format]
Gary Krockover

DOWNLOAD WEBDNA NOW!

Top Articles:

F.A.Q

A compilation of some user's questions...

WebDNA Modules

A list of the currently available modules...

WebDNA reference

A list of all WebDNA instructions...

AWS Raw WebDNA LAMP-Plus WebServer

Amazon Web Services (AWS) README for Machine Image ID...

WebDNA Libraries

A list of available libraries for WebDNA...

Tips and Tricks

A list of user-submitted tips ...

Related Readings:

random password-generator code

Generate a random alpha-numeric string...

Do you hate updating the copyright notice at the bottom of all your pages?

It's January 1st and you have to update the copyright notice at the bottom of all your websites...

Cloning a Record

Often...

Annoying character on writefile

How do I get rid of or convert the line feed character during a writefile?...

ImageMagick

Use ImageMagick to manipulate images when you upload them...

Using a simple Array of Variables with [interpret]

The [interpret] context is very powerful command in the hands of a skilled WebDNA programmer...