This is the prompt I am working from:
In the state population data, can you write a loop that pulls only states with populations between 200,000 and 250,000 in 1800? You could accomplish this a few different ways. Try to use next and break statements.
The dataset in question tracks how each state's population has shifted from year to year, decade to decade.
There are various columns representing each year of observations, including one for 1800 ("X1800"). The states are all also listed under one column ("state," of course).
I've been working on this one for quite a while, being new to coding. Right now, the code I have is as follows:
i <- 1
for (i in 1:length(statepopulations$X1800)) {
if ((statepopulations$X1800[i] < 200000) == TRUE)
next
if ((statepopulations$X1800[i] > 250000) == TRUE)
break
print (statepopulations$state[i])
}
I want to print the names of all states that fall within that population range for the year 1800.
I'm not sure where I'm going wrong. Any help is appreciated.
I keep getting a message that I'm "missing value where TRUE/FALSE needed."
in the condition, you don't need the == TRUE part.
(statepopulations$X1800[i] < 200000) should work by itself -- it will return a TRUE or FALSE, which will dictate what happens next
So I'm extracting data from a rasterbrick I made using the method from this question: How to extract data from a RasterBrick?
In addition to obtaining the data from the layer given by the date, I want to extract the data from months prior. In my best guess I do this by doing something like this:
sapply(1:nrow(pts), function(i){extract(b, cbind(pts$x[i],pts$y[i]), layer=pts$layerindex[i-1], nl=1)})
So it the extracting should look at layerindex i-1, this should then give the data for one month earlier. So a point with layerindex = 5, should look at layer 5-1 = 4.
However it doesn't do this and seems to give either some random number or a duplicate from months prior. What would be the correct way to go about this?
Your code is taking the value from the layer of the previous point, not the previous layer.
To see that imagine we are looking at the point in row 2 (i=2). your code that indicates the layer is pts$layerindex[i-1], which is pts$layerindex[1]. In other words, the layer of the point in row 1.
The fix is easy enough. For clarity I will write the function separetely:
foo = function(i) extract(b, cbind(pts$x[i],pts$y[i]), layer=pts$layerindex[i]-1, nl=1)
sapply(1:nrow(pts), foo)
I have not tested it, but this should be all.
I would like to create a function that looks at a column of values. from those values look at each value individually, and asses which of the other data points value is closest to that data point.
I'm guessing it could be done by checking the length of the data frame, making a list of the respective length in steps of 1. Then use that list to reference which cell is being analysed against the rest of the column. though I don't know how to implement that.
eg.
data:
20
17
29
33
1) is closest to 2)
2) is closest to 1)
3) is closest to 4)
4) is closest to 3)
I found this example which tests for similarity but id like to know what letter is assigns to.
x=c(1:100)
your.number=5.43
which(abs(x-your.number)==min(abs(x-your.number)))
Also if you know how I could do this, could you expain the parts of the code and what they mean?
I wrote a quick function that does the same thing as the code you provided.
The code you provided takes the absolute value of the difference between your number and each value in the vector, and compares that the minimum value from that vector. This is the same as the which.min function that I use below. I go through my steps below. Hope this helps.
Make up some data
a = 1:100
yourNumber = 6
Where Num is your number, and x is a vector
getClosest=function(x, Num){
return(which.min(abs(x-Num)))
}
Then if you run this command, it should return the index for the value of the vector that corresponds to the closest value to your specified number.
getClosest(x=a, Num=yourNumber)
I'm new to R and my problem is I know what I need to do, just not how to do it in R. I have an very large data frame from a web services load test, ~20M observations. I has the following variables:
epochtime, uri, cache (hit or miss)
I'm thinking I need to do a coule of things. I need to subset my data frame for the top 50 distinct URIs then for each observation in each subset calculate the % cache hit at that point in time. The end goal is a plot of cache hit/miss % over time by URI
I have read, and am still reading various posts here on this topic but R is pretty new and I have a deadline. I'd appreciate any help I can get
EDIT:
I can't provide exact data but it looks like this, its at least 20M observations I'm retrieving from a Mongo database. Time is epoch and we're recording many thousands per second so time has a lot of dupes, thats expected. There could be more than 50 uri, I only care about the top 50. The end result would be a line plot over time of % TCP_HIT to the total occurrences by URI. Hope thats clearer
time uri action
1355683900 /some/uri TCP_HIT
1355683900 /some/other/uri TCP_HIT
1355683905 /some/other/uri TCP_MISS
1355683906 /some/uri TCP_MISS
You are looking for the aggregate function.
Call your data frame u:
> u
time uri action
1 1355683900 /some/uri TCP_HIT
2 1355683900 /some/other/uri TCP_HIT
3 1355683905 /some/other/uri TCP_MISS
4 1355683906 /some/uri TCP_MISS
Here is the ratio of hits for a subset (using the order of factor levels, TCP_HIT=1, TCP_MISS=2 as alphabetical order is used by default), with ten-second intervals:
ratio <- function(u) aggregate(u$action ~ u$time %/% 10,
FUN=function(x) sum((2-as.numeric(x))/length(x)))
Now use lapply to get the final result:
lapply(seq_along(levels(u$uri)),
function(l) list(uri=levels(u$uri)[l],
hits=ratio(u[as.numeric(u$uri) == l,])))
[[1]]
[[1]]$uri
[1] "/some/other/uri"
[[1]]$hits
u$time%/%10 u$action
1 135568390 0.5
[[2]]
[[2]]$uri
[1] "/some/uri"
[[2]]$hits
u$time%/%10 u$action
1 135568390 0.5
Or otherwise filter the data frame by URI before computing the ratio.
#MatthewLundberg's code is the right idea. Specifically, you want something that utilizes the split-apply-combine strategy.
Given the size of your data, though, I'd take a look at the data.table package.
You can see why visually here--data.table is just faster.
Thought it would be useful to share my solution to the plotting part of them problem.
My R "noobness" my shine here but this is what I came up with. It makes a basic line plot. Its plotting the actual value, I haven't done any conversions.
for ( i in 1:length(h)) {
name <- unlist(h[[i]][1])
dftemp <- as.data.frame(do.call(rbind,h[[i]][2]))
names(dftemp) <- c("time", "cache")
plot(dftemp$time,dftemp$cache, type="o")
title(main=name)
}
I have some data formatted as below. I have done some analysis on this and would like to be able to plot the price development in the same graph as the analyzed data.
This requires me to have the same x-axes for the data.
So I would like to aggregate the "shares" column in say 150 increments, and add the "finalprice" and "time" to this.
The aggregation should include the latest time and price, so if the aggregation needs to occur over two or more rows of data then the last row should provide the price and time data.
My question is how to create a new vector with 150 shares per row.
The length of the vector will equal sum(shares)/150.
Is there an easy way to do this? Thanks in advance.
Edit:
I thought about expanding the observations using rep(finalprice, shares) and then getting each 150th value of the expanded vector.
Data sample:
"date","ord","shares","finalprice","time","stock"
20120702,E,2000,99.35,540.84753333,500
20120702,E,28000,99.35,540.84753333,500
20120702,E,50,99.5,542.03073333,500
20120702,E,13874,99.5,542.29411667,500
20120702,E,292,99.5,542.30191667,500
20120702,E,784,99.5,542.30193333,500
20120702,E,13300,99.35,543.04805,500
20120702,E,16658,99.35,543.04805,500
20120702,E,42,99.5,543.04805,500
20120702,E,400,99.4,546.17173333,500
20120702,E,100,99.4,547.07,500
20120702,E,2219,99.3,549.47988333,500
20120702,E,781,99.3,549.5238,500
20120702,E,50,99.3,553.4052,500
20120702,E,1500,99.35,559.86275,500
20120702,E,103,99.5,567.56726667,500
20120702,E,1105,99.7,573.93326667,500
20120702,E,4100,99.5,582.2657,500
20120702,E,900,99.5,582.2657,500
20120702,E,1024,99.45,582.43891667,500
20120702,E,8214,99.45,582.43891667,500
20120702,E,10762,99.45,582.43895,500
20120702,E,1250,99.6,586.86446667,500
20120702,E,5000,99.45,594.39061667,500
20120702,E,20000,99.45,594.39061667,500
20120702,E,15000,99.45,594.39061667,500
20120702,E,4000,99.45,601.34491667,500
20120702,E,8700,99.45,603.53608333,500
20120702,E,3290,99.6,609.23213333,500
I think I got it solved.
expand <- rep(finalprice, shares)
Increment <- expand[seq(from = 1, to = length(expand), by = 150)]