How to do it...
The first piece of data we want to obtain is a snapshot of the stocks we want to analyze. One of the best ways to do this is to download data from one of the many stock screener applications that exist. Our favorite screener to download stock data from belongs to http://finviz.com.
Let's acquire the stock market data that we will use for this chapter with the help of the
following steps:
- First, let's pull up finviz stock screener available at http://finviz.com/screener.ashx:
As you can see, the site has multiple fields that can be filtered. If you click on the All tab, you can see all of the fields that can be displayed.
- For this project, we want to export all the fields for all the companies in the screener. You can either customize the screener by checking 69 check-boxes, at the time of writing, or you can use the following URL to make all the fields show up automatically:
You should now see the screener with all the available fields.
- If you scroll all the way to the bottom right of the screen, there should be an export link. Click on this link and save the CSV file as finviz.csv.
- Finally, we will launch RStudio, read the finviz.csv file from the path where we saved it, and assign it to a data frame, as follows:
finviz <- read.csv("path/finviz.csv")
In data analysis, it is always better for each step that is performed to be in code instead of as a series of point-and-click actions that require human intervention. This way, it is much easier and faster to reproduce your results.
- After going through steps 1 to 4 for the first time (and some clever reading of
URLs from our browser), we can replace the previous lines of code with the following two commands:
url_to_open <-
'http://finviz.com/export.ashx?v=152&c=0,1,2,3,4,5,6,7,8,9,10,
11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,5
2,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68'
finviz <- read.csv(url(url_to_open))
Note the structure of the URL in step 2; it contains a comma-separated list of the check-boxes we wish to select. You can programmatically generate this URL to easily select whichever combination of companies' data you want to download.
If you want to avoid typing the numbers 0 through 68, you can use a combination of the sprintf and paste commands to accomplish the same thing:
url_to_open <-
sprintf("http://finviz.com/export.ashx?v=152&c=%s", paste(0:68, collapse = ","))
If you want to avoid typing the numbers 0 through 68, you can use a combination of the sprintf and paste commands to accomplish the same thing:
url_to_open <-
sprintf("http://finviz.com/export.ashx?v=152&c=%s", paste(0:68, collapse = ","))