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Insert random NAs in a vector in R

I was recently writing a function which was going to need to deal with NAs in some kind of semi-intelligent way. I wanted to test it with some fake data, meaning that I was going to need a vector with some random NAs sprinkled in. After a few disappointing google searches and a stack overflow post or two that left something to be desired, I sat down, thought for a few minutes, and came up with this.

#create a vector of random values
 foo <- rnorm(n=100, mean=20, sd=5)
#randomly choose 15 indices to replace
#this is the step in which I thought I was clever
#because I use which() and %in% in the same line
 ind <- which(foo %in% sample(foo, 15))
#now replace those indices in foo with NA
 foo[ind]<-NA
#here is our vector with 15 random NAs 
 foo

Not especially game changing but more elegant than any of the solutions I found on the interwebs, so there it is FTW.

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GIS in R: Part 1

I messed around with R for years without really learning how to use it properly. I think it’s because I could always throw my hands up when the going got tough and run back and cling the skirts of Excel or JMP or Systat. I finally learned how to use R when I needed to do a fairly hefty GIS project and I didn’t have access to a computer with ArcGIS and couldn’t afford to buy it (who can?). So I started looking into R’s spatial abilities.

Admittedly R might not be the most obvious choice for free GIS options, combinations of QGIS (http://www.qgis.org/), GRASS (http://grass.osgeo.org/), PostGIS (http://postgis.refractions.net/), or OpenGeo (http://boundlessgeo.com/solutions/opengeo-suite/download/) might pop up in google searches before R. R might not even be the first general purpose programming language you think of for GIS, especially now that ArcGIS relies on Python for much of its modeling. However, all of these tools have a significant learning curve, and I was farther along in R than any of these alternatives, so I started googling and watching tutorial videos. So should you be using R for analyzing and displaying spatial data? If you already know a little or a lot of R, if you need a cross platform solution, or need to do some fairly heavy stats applications to your spatial data, R just might be a good solution for you. It turns out R has lots of support for spatial data and does a great job displaying it too.

There are a number of packages useful for analyzing and displaying your spatial data. I think the 4 most useful right out of the gate are sp, rgdal, maptools, and raster. If you haven’t installed packages before do this…

install.packages(“sp”)
install.packages(“raster”)
install.packages(“maptools”)

…and if you are on a Windows machine…

install.packages(“rgdal”)

If you’re on a Mac, installing rgdal is a little tricky. Give this a try

setRepositories(ind=1:2)
install.packages(“rgdal”)

If that doesn’t work read this over.
http://blog.fellstat.com/?p=46

After installing the packages, if you want to use the functions contained in that package you need to load the library. To use the functions in the sp package, you should type

library(sp)

to load the rgdal package…

library(rgdal)

etc.

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Science link fest for the week of the 27th

Hello Paleoposse! This week I bring you Egyptians and iron meteorites, Neil deGrasse Tyson as the Carl Sagan of our generation and a mild rant about poor quality science reporting. I’m off to enjoy my 30th birthday. Hope you all have an awesome weekend!

Solid science:

  • Here’s a story that’s near and dear to my heart: the first use of iron in Egyptian history came from a meteorite. I really love this article as it’s the perfect combination of science and history and it’s written (mostly) free of jargon. And it’s free through Meteoritics and Planetary Science
  • Continuing with the news on space stuff, this article from Scientific American talks about Comet ISON and how studying it can yield clues about the formation of our solar system.
  • One of my favorite geologists, and personal friend, Dana Hunter, has a great story about the glacier-sculpted geology of Discovery Park in Seattle. She focuses mostly on the South Bluff, which is this thick with layers of mud and sand that record the formation of the Sound. And there’s a picture of the back of my head from my last trip when she gave a tour of the area.

Continue Reading →

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Your science links for the week of July 19th

Howdy paleoposse! Here are this weeks sciency links for your weekend reading pleasure.  This weeks links cover gold producing neutron stars, the boredom of travelling to Mars, some words of inspiration from Richard Feynman, and Comic-Con 2013.

Things that are science:

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Science link goodness for the week of July 12th

Hello paleoposse! This week I bring you some of my favorite science articles from around the internet. In keeping with the podcast theme, I’ve divided it up into things that are science, things that are sort of science, and things that wish they were science. This week we cover everything from chondrules to volcanoes to the science of the Flash and even a crazy preacher.

Things that are science…

  • One of the more enduring controversies in meteoritics is how the rounded silicate inclusions in chondrites, chondrules, were produced. Some have argued that they condensed from the early solar nebula, while others contend that they originated from the guts of the earliest exploded planetesimals. The latter explanation is gaining momentum.
  • Slate has an excellent article on why testicles are kept in such a vulnerable position on most mammals.
  • National Geographic brings us some gorgeous photos of the Mexican volcano, Popocatepetl.
  • This article from BBC News looks at the science of pessimism and how one can become an optimist. Take some of it with a grain of salt, but still a fun read.
  • Astronomers are working to figure out the origin of radio bursts that occur nearly every second every day. Some proposed ideas are evaporating black holes (my personal favorite) or black holes devouring neutron stars.
  • Forget the Six Million Dollar Man. Bring on the new super food, the five million dollar broccoli! 

Things that are sort of science…

And things that wish they were science…

  • In keeping with the “things that wish they were science” theme, io9 has a post about a preacher that’s convinced the new Star Trek movie will lead humans to really love their animals.
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