R: how to avoid explicit names when using a variable

Question

I have the following code in R:

library(quantmod)

mySymbol = "^STOXX50E"
getSymbols(mySymbol, from="2004-01-01", to=Sys.Date())

chartSeries(Cl(STOXX50E))

which simply download the time series for the inder Eurostoxx and then plots the closing price. It works as expected. Anyway, I was wondering how I can avoid to write explicitely "STOXX50E" everytime I want to reference to this variable. For example, I would like to be able to reference the variable that contains the data with a generic name like "INDEX" so that I don't need to change all the calls when I want to launch the code with another inder.

For example, if i want to download and plot the closing price for the S&P500 I have to do:

library(quantmod)

mySymbol = "^GSPC"
getSymbols(mySymbol, from="2004-01-01", to=Sys.Date())

chartSeries(Cl(GSPC))

so I have to change the variable name not only on the second line but also on the last. I would rather something more generic like:

library(quantmod)

mySymbol = "^GSPC"
getSymbols(mySymbol, from="2004-01-01", to=Sys.Date())

chartSeries(Cl(mySymbol))

So that once I have set the name for mySymbol I don't have to change all the rest of the code. But this doesn't work. How can I accomplish this?

score 3 · Answer 1 · answered May 09 '15 at 22:16

An alternative to the currently accepted solution is to use auto.assign=FALSE in your call to getSymbols.

library(quantmod)
mySymbol <- "^STOXX50E"
x <- getSymbols(mySymbol, from="2004-01-01", to=Sys.Date(), auto.assign=FALSE)
chartSeries(Cl(x), name=mySymbol)
# If you want to remove the "^" from the name:
chartSeries(Cl(x), name=sub("^","",mySymbol,fixed=TRUE))

I prefer this solution because I find the coder clearer and easier to understand.

LyzandeR · Accepted Answer · 2015-05-08T22:46:37.507

1

You can do it this way:

library(quantmod)

mySymbol = "^STOXX50E"
getSymbols(mySymbol, from="2004-01-01", to=Sys.Date())

chartSeries(Cl(get(substring(mySymbol,2,nchar(mysymbol)))))

If you want to change the title of the plot do:

chartSeries(Cl(get(substring(mySymbol,2,nchar(mysymbol)))), name=mySymbol)

Essentially when you use getSymbols a variable named STOXX50E is stored on your global environment which contains the data. Using get you can access a variable name by providing a string i.e. "^STOXX50E". I then use substring to avoid the first character of the variable mySymbol which is ^.

And it works. You essentially change mySymbol and the code runs without having to alter anything else!

enter image description here

EDIT:

This is probably a better way in terms that the code is more readable and you avoid the annoying ^ in the title:

library(quantmod)

mySymbol = "STOXX50E"
getSymbols(paste('^',mySymbol,sep=''), from="2004-01-01", to=Sys.Date())

chartSeries(Cl(get(mySymbol)),name=mySymbol)

enter image description here

edited May 08 '15 at 22:46

answered May 08 '15 at 22:39

LyzandeR

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1

That is great! Thank you. Do you also know how to remove the title name in the chart. Now, after your fix, the name is very long... – opt May 08 '15 at 22:46
1

You are welcome! I updated my answer. In order to change the name you pass in the `name` argument. – LyzandeR May 08 '15 at 22:49
1

I also provided an edit with a clearer solution which I think looks prettier. It uses `paste` for the `getSymbols` function (to add `^`) and then only uses `get` in a simple way for `chartSeries`. – LyzandeR May 08 '15 at 22:51
1

Oh and if you want to remove the name completely just use `''` as the name. – LyzandeR May 08 '15 at 22:53
1

Great. Problem solved and thanks to you I learnt something new. – opt May 08 '15 at 22:56
Really glad I could be of help :) !! – LyzandeR May 08 '15 at 22:57

R: how to avoid explicit names when using a variable

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