Unable to program a loop for regression analysis in R - r

Question

I have a problem with my R code. I would like to run about 100 regressions and perform this process with a loop. I have tried to program the loop myself using help from YouTube and the like, but I am getting nowhere. Therefore, I would like to ask you if you can help me.
Specifically, it's about the following:
I have a dataset of the 100 companies in the Nasdaq100 and I would like to regress the sales per share with the stock price performance on a quarterly basis. Another problem is that the data set contains these 100 companies and a subset with the respective ticker symbol has to be created for each additional company so that R can access it correctly for each regression.
Here is an excerpt from the code:
Nasdaq_100 = read_xlsx("Nasdaq_100_Sales_Data.xlsx")
#Correlation between quarterly close price and Sales of AMD
AMD <- subset (Nasdaq_100, Nasdaq_100$TickerSymbol=="AMD")
AMD_regression = lm(AMD$Sales ~ AMD$Stockprice_quarterly, data = Nasdaq_100)
summary(AMD_regression)
Can you help me to program this loop for regression analysis?
Thanks in advance for any help!

Answer 1

To convert this to a for loop, first get a list of the .xlsx files in your working directory:
require(data.table)
myfiles <- list.files(pattern="*.xlsx")
Then loop through each file, and saving with minor modifications to your existing code:
for (file in myfiles) {
Nasdaq_100 <- data.table::fread(file)
AMD <- subset (Nasdaq_100, Nasdaq_100$TickerSymbol=="AMD")
AMD_regression = lm(AMD$Sales ~ AMD$Stockprice_quarterly, data = Nasdaq_100)
summary(AMD_regression)
data.table::fwrite(AMD_regression, file=paste0("output_", file), quote = F, sep = "\t", row.names = F)
}
Copy-paste in r and Let me know if it works.

Answer 2

file <- choose.files()
lmset <- data.frame(x='x',y='y')
for(i in seq_len(100))
{
data <- read_excel(file,sheet=i)
lmset <- rbind(lmset,lm(AMD$Sales~AMD$Stockprice_quarterly,data=data)$coefficients)
}