2767 search results for "GIS"

unsupervised classification of a raster in R: the layer-stack or part one.

July 29, 2012
By
unsupervised classification of a raster in R: the layer-stack or part one.

In my last post I was explaining the usage of QGis to do a layerstack of a Landsat-scene. Due to the fact that further research and trying out resulted in frustration I decided to stick with a software I know well: R. So download the needed layers here and open up your flavoured version of

Read more »

Hi R and Axys, I’m d3.js “Nice to Meet You” (On the Iphone)

July 27, 2012
By
Hi R and Axys, I’m d3.js “Nice to Meet You” (On the Iphone)

I am still definitely in the proof of concept stage, but as I progress I get more excited about the prospects of combining d3.js with R and Axys through Bryan Lewis’ really nice R websockets package (even nicer now that he has added the daemonize fun...

Read more »

Linear regression by gradient descent

July 26, 2012
By
Linear regression by gradient descent

In Andrew Ng's Machine Learning class, the first section demonstrates gradient descent by using it on a familiar problem, that of fitting a linear function to data. Let's start off, by generating some bogus data with known characteristics. Let's make y just a noisy version of x. Let's also add 3 to give the intercept term something to...

Read more »

Universal portfolio, part 9

July 25, 2012
By
Universal portfolio, part 9

Part 8 was discussing the distribution of the absolute wealth of the Universal Portfolio across all possible tuples of length 2, 3 and 4.However, comparing the absolute wealth against some reference, especially against simple portfolio selection algor...

Read more »

Getting rasters into shape from R

July 25, 2012
By
Getting rasters into shape from R

Today I needed to convert a raster to a polygon shapefile for further processing and plotting in R. I like to keep my code together so I can easily keep track of what I’ve done, so it made sense to … Continue reading →

Read more »

Inspirational Stack Overflow Dendrogram Applied to Currencies

July 25, 2012
By
Inspirational Stack Overflow Dendrogram Applied to Currencies

When I saw the answer to this Stack Overflow question, I immediately remembered working on my old post Clustering with Currencies and Fidelity Funds and just had to try to apply this technique.  As I should have guessed, it worked with only a mini...

Read more »

Measuring persistence in a time series : Application of rolling window regression

Measuring persistence in a time series : Application of rolling window regression

During my final semester at IGIDR I did a project paper in macroeconomics involving timeseries econometrics. The concept that I focused on my study was unit root, which I have touched upon in my earlier posts. This study presents a novel...

Read more »

How to tell when error bars correspond to a significant p-value

July 24, 2012
By
How to tell when error bars correspond to a significant p-value

Can you tell when error bars based on 95 % CIs or standard errors correspond to a significant p-value? Don’t fret if you think it’s hard, a study from 2005 showed that researchers in psychogoly, behavior neuroscience and medicine had a hard time judging when error bars from two independent groups signified a significant difference.

Read more »

get UCSC images for a list of regions in batch

July 24, 2012
By

Here is my working R code for the task. It can be simplified as 3 lines.# example of controling individual track#theURL="http://genome.ucsc.edu/cgi-bin/hgTracks?db=mm9&wgRna=hide&cpgIslandExt=pack&ensGene=hide&mrna=hide&intronEst=hi...

Read more »

The Failure of Asset Allocation – Bonds Are An Imperfect Hedge

July 24, 2012
By
The Failure of Asset Allocation – Bonds Are An Imperfect Hedge

US investors were spoiled by US Treasuries which acted as a near perfect hedge to stocks during the 2008-2009 crisis.  However, in real crisis, bonds rarely offer any comfort, and asset allocation fails (see post Death Spiral of a Country and IMF ...

Read more »