Monthly Archives: July 2017

Visa Fun

Hello avid readers. Unfortunately I do not have a post ready for this Monday as I’ve had to spend the whole day on visa application issues. I recently discovered that a Post Doc visa does not fall under the umbrella of the study visa, as I had been led to believe. Instead one must acquire a Scarce Skills Visa, which is a type of proper work visa. This then requires quite a bit more paperwork and several more steps than the renewal of a study visa.

I can happily say however that the systems in place for visa facilitation have definitely improved since my last visa application in 2014. Not just in SA either. More and more things are able to be completed without the need for couriers. This is always great as mailing things internationally is always the slowest least certain part of the compiling of the supporting documents.

I’ll see if I can’t get a post up later this week with some pretty environmental figures.

Mapping with ggplot2

Objective

There are many different things that require scientists to use programming languages (like R). Far too many to count here. There is however one common use amongst almost all environmental scientists: mapping. Almost every report, research project or paper will have need to refer to a study area. This is almost always “Figure 1”. To this end, whenever I teach R, or run workshops on it, one of the questions I am always prepared for is how to create a map of a particular area. Being a happy convert to the tidyverse I only teach the graphics of ggplot2. I have found that people often prefer to use the ggmap extension to create ggplot quality figures with Google map backgrounds, but I personally think that a more traditional monotone background for maps looks more professional. What I’ve decided to showcase this week is the data and code required to create a publication quality map. Indeed, the following code will create the aforementioned obligatory “Figure 1” in a paper I am currently preparing for submission.

Data

There are heaps of packages etc. that one may use to create maps. And there is a never ending source of blogs, books and tutorials that illustrate many of the different ways to visualise spatial data. For my international and geographic borders I prefer to use data I’ve downloaded from GSHHSG and then converted to dataframes using functions found in the PBSmapping package. I then save these converted dataframes as .Rdata objects on my computer for ease of use with all of my projects. For the domestic borders of a country, which I won’t use in this post, one may go here. Note however that for some strange reason this website still has the pre-1994 borders for South Africa. For the correct SA borders one must go here. The current SA borders may actually be download in the .Rdata format, which is neat.

Once one has the borders to be used in the map, the next step is to think about what one actually wants to show. The main purpose of this map is to show where several in situ coastal seawater temperature time series were collected. This could be done quite simply but a plain black and white map is offensively boring so we want to make sure there is a good amount of (but not too much!) colour in order to entice the reader. I personally find pictures of meso-scale oceanic phenomena particularly beautiful so try to include them whenever I can. Luckily that is also what I study so it is not strange that I include such things in my work. Now if only I studied panda’s, too…

Panda’s aside, the current work I am engaged in also requires that the atmospheric processes around southern Africa be considered in addition to the oceanography. To visualise both air and sea concurrently would be a mess so we will want to create separate panels for each. Because I have been working with reanalysis data lately, and not satellite data, I am also able to include the wind/ current vectors in order to really help the temperature patterns pop. The oceanic data are from the BRAN2016 product and the atmospheric data are from ERA-Interim. Both of which are available for download for free for scientific pursuits. I’ve chosen here to use the mean values for January 1st as the summer months provide the most clear example of the thermal differences between the Agulhas and Benguela currents. The code used to create the scale bar in the maps may be found here. It’s not a proper ggplot geom function but works well enough. I’ve also decided to add the 200 m isobath to the sea panel. These data come from NOAA.

Mapping

I find that it is easier to keep track of the different aspects of a map when they are stored as different dataframes. One should however avoid having too many loose dataframes running about in the global environment. It is a balancing act and requires one to find a happy middle ground. Here I am going to cut the all_jan1_0.5 dataframe into 4. One each for air and sea temperatures and vectors. I am also going to reduce the resolution of the wind so that the vectors will plot more nicely.

With just a few alterations to our nicely divided up dataframes we are ready to create a map. We will look at the code required to create each map and then put it all together in the end.

First up is the most busy. The following code chunk will create the top panel of our map, the sea state. It is necessary to label all of the locations mentioned in the text and so they are thrown on here. In order to make the site label easier to read I’ve made them red. This is particularly jarring but I think I like it.

Many of the sites that need to be plotted are laying on top of each other. This is never good, but is made worse when the sites in question are refereed to frequently in the text. For this reason we need to create a little panel inside of the larger figure that shows a zoomed in picture of False Bay. Complete with text labels.

We could possibly create another inset panel for the clomp of sites around Hamburg but this figure is already getting too busy. So we’ll leave it for now. One inset panel will serve to illustrate the code necessary to create a faceted map so for the purposes of this post it will also suffice. That leaves us with only the bottom panel to create. The air state. I’ve decided to put the scale bar/ North arrow on this panel in an attempt to balance the amount of information in each panel.

With our three pieces of the map complete, it is time to stick them together. There are many ways to do this but I have recently found that using annotation_custom allows one to stick any sort of ggplot like object onto any other sort of ggplot object. This is an exciting development and opens up a lot of doors for some pretty creative stuff. Here I will just use it to demonstrate simple faceting, but combined with panel gridding. Really though the sky is the limit.

Summary

The developments in the gridding system have brought the potential for using ggplot for these more complex maps forward quite a bit. As long as one does not use a constrained mapping coordinate system (i.e. coord_fixed) the grob-ification of the ggplot objects seems to allow the placing of the pieces into a common area to be performed smoothly. Displaying many different bits of information cleanly is always a challenge. This figure is particularly busy, out of necessity. I think it turned out very nicely though.

 

Figure 1: Map showing the southern tip of the African continent. The top panel shows the typical sea surface temperature and surface currents on January 1st. The bottom panel likewise shows the typical surface air temperatures and winds on any given January 1st.

Goats per Capita

Objective

A few weeks ago for a post about the relationship between gender equality and GDP/ capita I found a nifty website that has a massive amount of census information for most countries on our planet. Much of this information could be used to answer some very interesting and/ or important questions. But some of the data can be used to answer seemingly pointless questions. And that’s what I intend to do this week. Specifically, which countries in the world have the highest rates of goats/ capita?

Data

The goats per capita data were downloaded from the clia-infra website. These data are already in the format we need so there is little to be done before jumping straight into the analysis. We will however remove any records from before 1900 as these are almost entirely estimates, and not real records.

 

Analysis

First of all, I would like to know what the global trend in goats/ capita has been since 1900. To do so we need to create annual averages and apply a simple linear model to them. We will also plot boxplots to give us an idea of the spread of goats/ capita over the world.

 

Figure 1: Boxplots with a fitted linear model showing the global trend in goats/ capita over the last century.

 

As we may see in Figure 1, the overall trend in goats/ capita in the world has been decreasing very slightly over the last century. The striking result from Figure 1 however is the massive range of values as seen by the outliers from the boxplots. So which countries are these that have so many more goats/ capita than the rest of the world?

We want to see which countries have the most goats/ capita but there are 172 unique countries in this dataset so it would look much too busy to plot them all. To that end we want only the top and bottom 10 countries from the most recent year of reporting (2010).

 

 

Figure 2: Line graphs showing the rate of goats/ capita for the top and bottom 10 goat having countries in the world over the last century.

 

Summary

I was a bit surprised to find that Mongolia is far and away the country with the most goats/ capita at 5.140 in 2010. Less surprising is that the other top 9 goat having countries in the world in 2010 were all in Africa and their rate of goats/ capita was between 1.634 (Mauritania) to 0.124 (South Africa). This makes for a massive spread in what is already an outlying set of countries. How is it that Mongolia has so many more goats/ capita? This is a very odd result but the data were reported annually from 2000 to 2010 and they consistently show similarly high rates for Mongolia.

The bottom 10 goat having countries in the world are a mix of European, Asian, North American and Pacific Islands. This mix is not surprising as we may see in Figure 1 that there are no outliers in the bottom of the distribution. The highest value for the bottom 10 countries in 2010 was Tonga at 0.121. This is very close to the lowest value from the top 10 countries, and shows us that most of the 172 countries in this dataset have ~0.12 goats per person. With this average in mind, we see that the other bottom nine countries in Figure 2 really are much lower than the global average with rates approaching 0 goats/ capita. It is worth mentioning that the lowest overall rate of goats/ capita in 2010 was Japan at 0.0001. Meaning that there is only one goat in Japan for every 10,000 people. As opposed to Mongolia that has more than five goats for every one person. Therefore there were 50,000 times more goats/ capita in Mongolia than Japan in 2010…

I supposes the take away message from this analysis is that if one ever wants to get away from it all and just go spend time with a lot of goats, Mongolia is the place for you!

(and definitely avoid Japan)

 

US Parties and Immigration

Objective

As an immigrant myself, all of the talk of immigration to be found in main stream media outlets today makes me a bit nervous. Whereas most people that speak of the pro’s and con’s of immigration do so from the point of view of how it may affect the country of their birth, I view this issue as something that affects my ability to live outside the country of my birth. I immigrated into the Republic of South Africa in 2013 and have been living here since. I would do a piece on South African immigration but the numbers are difficult to get a hold of and honestly most people are less interest in South Africa than the USA.

Immigration is not a new talking point. It’s something that comes up in political and a-political circles all of the time. The current debate on the Muslim Ban in the USA may have reached a new level for this sort of rhetoric in the West, but targeted crackdowns of this sort are not new in the world. I won’t bother with citations here, but if one is interested a quick google of “xenophobia” + “border control” should yield some convincing results. As this current row of immigration debates in the USA has become so partisan, I decided that an interesting question to ask would be “Under which of the two parties have more people immigrated into the USA?” and “Under which of the two parties have more people been removed from the USA?”

Data

The historical data on immigration into the USA are located at the Department of Homeland Securities website. In 2013 the DHS started keeping very detailed reports of all immigration by age, country, marital status, etc. These highly detailed data are very interesting but will not help us to ask our central questions. We want long time series of data so that we may compare many different administrations from each party. For ease of analysis I have chosen to classify the party in power at any point in time based on the party of the President. I understand that the Senate or Congress would perhaps be better, if not more egalitarian choices, but the current focus of this issue has the US President at it’s core, so I decided to keep that theme constant in this analysis. I’ll only start from Eisenhower and go up until Obama as the publicly available DHS data end in 2015. They begin as far back as 1892, but ggplot2 has built into it a US president dataframe and I am going to just use that because I’m lazy.

 

Immigration

In this first figure we are defining immigration as the number of people actually receiving a green card in any given year. This is the most strict definition of “immigration” and I think may be best used to show whom the USA was choosing to let in.

 

Figure 1: Bar charts showing the number of green cards granted each year in the USA. The colour of the bars show the ruling party at the time of issuance. A linear model is imposed in black.

 

We may see in Figure 1 that the all time high for the granting of green cards was during the four year administration of George Bush Senior. These values are so much higher than the other administrations that it leverages the linear model drawn on these data up past where it should normally be to show the more normal trend exhibited by all of the other administrations since Eisenhower. That being said, we actually see a bit of a turn down during the Obama administration, with the largest year of green card issuance during the George Bush Junior administration larger than any year under Obama. I find that surprising. Figure 1 also shows us that we can’t really directly compare the different administrations because as populations increase, so too will the number of people that want to immigrate. In a quick pinch however we may use the residuals from the linear model to give us a slightly better visualisation of how the parties stack up against one another.

 

 

Figure 2: The residuals from a linear model fitted to the data shown in Figure 1.

 

It appears as though whenever there was a Bush in office it was much easier to get a green card. And that Democrats generally made it more difficult to do so.

Expulsion

Now that we have seen that it is easier to enter the USA during a Republican presidency, let’s see under which party an illegal immigrant is most likely to be expelled. There are two different classes of expulsion: ‘Removal’ and ‘Return’. Removal means that a legal order was issued to remove the individual. Return means that the individual was likewise not legally in the states, but left of their own volition.

 

 

Figure 3: Two bar charts showing the rates of returns and removals for immigrants from the USA.

 

Figure 3 tells a very interesting story. In the top panel (Returns), we see that from 1953-55 (shortly after WWII) there were massive numbers of immigrants that returned to their home countries voluntarily. Then there is a period of increase leading up to the 80’s. This then follows a somewhat normal distribution, peaking in the late 90’s near the end of the Clinton administration before the peaceful return of immigrants drops steadily through the 8 years of Bush then Obama. The bottom panel (Removals) shows the reason for this apparent relaxation on immigrants. It isn’t that immigrants were being sent away less, but rather they began to be removed more forcefully than appears to have been the policy until something changed during the Clinton Administration. The rate of immigrants being removed became greater than those being returned in 2011 under Obama. Again we see a heavy hand on immigration during years with a Democratic president in office. It is hard to compare the parties on this issue as the policy of forcefully removing immigrants in favour of having them leave peacefully has only been in practice over three administrations (Clinton, Bush Jr. and Obama). That being said, it is worth noting that the y axes on these two figures are not the same. The increase in removals does not outweigh the decrease in returns. Overall the rate of expulsion of immigrants from the states declined during the Obama administration. And perhaps also Bush Jr.

It is fair criticism to point out that a green card may take several years to acquire. This means that when one begins the process of applying for a green card it may take so long that a different party will be in power by the time it is granted… or not. I would argue however that most of these parties (with the exception of Carter) are in office for eight year stretches. This is not meant to be a definitive analysis, but I think it has proven to be a rather interesting first step. I didn’t expect the data to look like this. George Bush Senior, saviour to immigrants, who would have thought.