## Standard Deviation in IDL

The built in IDL standard deviation function in IDL, STDDEV, uses the moment function which treats the standard deviation as a sample, rather than a population. A short programme can give us both options.

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Associate Professor in Space Environment at the University of Birmingham, creating the next generation space weather forecast models. Included on Forbes 30 Under 30 list.

# Category: IDL

IDL, Mathematics## Standard Deviation in IDL

IDL, Mathematics, Misc## Graphical Analysis of Grey’s Anatomy Viewing Figures

IDL## Newton’s Method for Solving the Inverse Geodesic Problem in IDL

IDL## Negative Array Index in IDL

IDL## OS Detection in IDL

IDL## Random number between two numbers in IDL

The built in IDL standard deviation function in IDL, STDDEV, uses the moment function which treats the standard deviation as a sample, rather than a population. A short programme can give us both options.

I recently started watching Grey’s Anatomy which I’ve been enjoying. However a friend of mine told me that the later episodes are not as good. So I thought I would have a look if the viewing figures reflected this.

There are a number of approaches to solve the inverse geodesic problem, this post provides the IDL code to use Newton’s method as described by Karney (2012) in ‘Algorithms for geodesics‘.

Chris blew my mind this morning when he showed me what happens if you use negative numbers to index an array in IDL (in versions lower than 8!). I would argue that it gives something that you don’t want, this is how you fix it.

A lot of what I do in IDL involves using paths all over the place, the problem is, I want my code to work in Windows or Linux, but we of course have that old problem of / v \.

Generating a random number, or an array of random numbers, between 0 and 1, in IDL is easy. Simply call upon RANDOMU. But how do you generate random numbers between two other numbers?