Loop over data frame rows
Imagine that you are interested in the days where the stock price of Apple rises above 117. If it goes above this value, you want to print out the current date and stock price. If you have a stock data frame with a date and apple price column, could you loop over the rows of the data frame to accomplish this? You certainly could!
Before you do so, note that you can get the number of rows in your data frame using nrow(stock). Then, you can create a sequence to loop over from 1:nrow(stock).
for (row in 1:nrow(stock)) {
price <- stock[row, "apple"]
date <- stock[row, "date"]
if(price > 117) {
print(paste("On", date,
"the stock price was", price))
}
}
[1] "On 2016-12-21 the stock price was 117.06"
[1] "On 2016-12-27 the stock price was 117.26"
This incorporates a number of things we have learned so far. If statements, subsetting vectors, conditionals, and loops! Congratulations for learning so much!
The stocks data frame is available for you to use.
This is a part of the course
“Intermediate R for Finance”
Exercise instructions
- Fill in the blanks in the for loop to make the following true:
priceshould hold that iteration's pricedateshould hold that iteration's date- This time, you want to know if
applegoes above116. - If it does, print the
dateandprice. - If it was below
116, print out thedateand print that it was not an important day!
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
# Loop over stock rows
for (row in 1:___) {
price <- stock[___, "___"]
date <- stock[___, "___"]
if(___ > ___) {
print(paste("On", ___,
"the stock price was", ___))
} else {
print(paste("The date:", ___,
"is not an important day!"))
}
}This exercise is part of the course
Intermediate R for Finance
Learn about how dates work in R, and explore the world of if statements, loops, and functions using financial examples.
Loops can be useful for doing the same operation to each element of your data structure. In this chapter you will learn all about repeat, while, and for loops!
Exercise 1: Repeat loopsExercise 2: Repeat, repeat, repeatExercise 3: When to break?Exercise 4: While loopsExercise 5: While with a printExercise 6: While with a plotExercise 7: Break itExercise 8: For loopsExercise 9: Loop over a vectorExercise 10: Loop over data frame rowsExercise 11: Loop over matrix elementsExercise 12: Break and nextWhat is DataCamp?
Learn the data skills you need online at your own pace—from non-coding essentials to data science and machine learning.