My data frame is SPData, which includes date, open price, closing price and volume for the S&P500 for the last 25 years (~ 250 days per year). 
Additionally, I have `SPData$Year`, which is simply a vector with the year from the date column stored numerically, from 1990 - 2015. 

```
library(dplyr)
SPData1990 <- filter(SPData, Year == 1990)

```

results in a data frame with ~250 observations, one for each trading day in 1990. I did this for all 25 years already.

Is there a way to create a formula that would save all the other data corresponding from each year as a new data frame (SPData1991, SPData 1992, SPData1993, etc.)? I was trying to think through a for(i in years) loop corresponding to the formula, `years <- unique(SPData$Year, FALSE)`, but I am not familiar enough with programming in general to figure this out.

Thanks