For Loop to Rename Column Names of Many Objects R - r

Question

I am looking for a way to rename the columns of several objects with a for loop or other method in R. Ultimately, I want to be able to bind the rows of each Stock object into one large data frame, but cannot due to differing column names. Example below:
AAPL <-
Date AAPL.Open AAPL.High AAPL.Low AAPL.Close AAPL.Volume AAPL.Adjusted Stock pct_change
2020-05-14 304.51 309.79 301.53 309.54 39732300 309.54 AAPL 0.61
2020-05-15 300.35 307.90 300.21 307.71 41561200 307.71 AAPL -0.59
GOOG <-
Date GOOG.Open GOOG.High GOOG.Low GOOG.Close GOOG.Volume GOOG.Adjusted Stock pct_change
2020-05-14 1335.02 1357.420 1323.910 1356.13 1603100 1356.13 GOOG 0.50
2020-05-15 1350.00 1374.480 1339.000 1373.19 1705700 1373.19 GOOG 1.26
For this example I have 2 objects (AAPL and GOOG), but realistically I would be working with many more. Can I create a for loop to iterate through each object, and rename the 2nd column of each to "Open", 3rd column to "High", 4th column to "Low",.... etc so I can then bind all these objects together?
I already have a column named "Stock", so I do not need the Ticker part of the column name.

Answer 1

Using quantmod we can read a set of stock ticker symbols, clean their names & rbind() into a single data frame.
There are three key features illustrated within this answer, including:
Use of get() to access the objects written by quantmod::getSymbols() once they are loaded into memory.
Use of the symbol names passed into lapply() to add a symbol column to each data frame.
Conversion of the dates stored as row names in the xts objects written by getSymbols() to a data frame column.
First, we'll use getSymbols() to read data from yahoo.com.
library(quantmod)
from.dat <- as.Date("12/02/19",format="%m/%d/%y")
to.dat <- as.Date("12/06/19",format="%m/%d/%y")
theSymbols <- c("AAPL","AXP","BA","CAT","CSCO","CVX","XOM","GS","HD","IBM",
"INTC","JNJ","KO","JPM","MCD","MMM","MRK","MSFT","NKE","PFE","PG",
"TRV","UNH","UTX","VZ","V","WBA","WMT","DIS","DOW")
getSymbols(theSymbols,from=from.dat,to=to.dat,src="yahoo")
# since quantmod::getSymbols() writes named data frames, need to use
# get() with the symbol names to access each data frame
head(get(theSymbols[[1]]))
> head(get(theSymbols[[1]]))
AAPL.Open AAPL.High AAPL.Low AAPL.Close AAPL.Volume AAPL.Adjusted
2019-12-02 267.27 268.25 263.45 264.16 23621800 262.8231
2019-12-03 258.31 259.53 256.29 259.45 28607600 258.1370
2019-12-04 261.07 263.31 260.68 261.74 16795400 260.4153
2019-12-05 263.79 265.89 262.73 265.58 18606100 264.2359
Having illustrated how to access the symbol objects in the global environment, we'll use lapply() to extract the dates from the row names, clean the column headings, and write the symbol name as a column for each symbol's data object.
# convert to list
symbolData <- lapply(theSymbols,function(x){
y <- as.data.frame(get(x))
colnames(y) <- c("open","high","low","close","volume","adjusted")
y$date <- rownames(y)
y$symbol <- x
y
})
Finally, we convert the list of data frames to a single data frame.
#combine to single data frame
combinedData <- do.call(rbind,symbolData)
rownames(combinedData) <- 1:nrow(combinedData)
...and the output:
> nrow(combinedData)
[1] 120
> head(combinedData)
open high low close volume adjusted date symbol
1 267.27 268.25 263.45 264.16 23621800 262.8231 2019-12-02 AAPL
2 258.31 259.53 256.29 259.45 28607600 258.1370 2019-12-03 AAPL
3 261.07 263.31 260.68 261.74 16795400 260.4153 2019-12-04 AAPL
4 263.79 265.89 262.73 265.58 18606100 264.2359 2019-12-05 AAPL
5 120.31 120.36 117.07 117.26 5538200 116.2095 2019-12-02 AXP
6 116.04 116.75 114.65 116.57 3792300 115.5256 2019-12-03 AXP
>

Answer 2

If you can guarantee the order of these columns this should do it:
for(df in list(AAPL, GOOG))
colnames(df) <- c("Date", "Open", "High", "Low", "Close", "Volume", "Adjusted", "Stock", "pct_change")

Answer 3

With lapply, we can loop over the list and remove the prefix in the column names with sub. This can be done without any external packages
lst1 <- lapply(list(AAPL, GOOG), function(x) {
colnames(x) <- sub(".*\\.", "", colnames(x))
x})