# Scaling Your Data in R: Understanding the Range

code
rtip
operations
Author

Steven P. Sanderson II, MPH

Published

April 3, 2024

# Introduction

Today, we’re diving into a fundamental data pre-processing technique: scaling values. This might sound simple, but it can significantly impact how your data behaves in analyses.

# Why Scale?

Imagine you have data on customer ages (in years) and purchase amounts (in dollars). The age range might be 18-80, while purchase amounts could vary from \$10 to \$1000. If you use these values directly in a model, the analysis might be biased towards the purchase amount due to its larger scale. Scaling brings both features (age and purchase amount) to a common ground, ensuring neither overpowers the other.

# The `scale()` Function

R offers a handy function called `scale()` to achieve this. Here’s the basic syntax:

``scaled_data <- scale(x, center = TRUE, scale = TRUE)``
• `data`: This is the vector or data frame containing the values you want to scale. A numeric matrix(like object)
• `center`: Either a logical value or numeric-alike vector of length equal to the number of columns of x, where ‘numeric-alike’ means that as.numeric(.) will be applied successfully if is.numeric(.) is not true.
• `scale`: Either a logical value or numeric-alike vector of length equal to the number of columns of x.
• `scaled_data`: This stores the new data frame with scaled values (typically one standard deviation from the mean).

# Example in Action!

Let’s see `scale()` in action. We’ll generate some sample data for height (in cm) and weight (in kg) of individuals:

``````set.seed(123)  # For reproducibility
height <- rnorm(100, mean = 170, sd = 10)
weight <- rnorm(100, mean = 70, sd = 15)
data <- data.frame(height, weight)``````

This creates a data frame (`data`) with 100 rows, where `height` has values around 170 cm with a standard deviation of 10 cm, and `weight` is centered around 70 kg with a standard deviation of 15 kg.

# Visualizing Before and After

Now, let’s visualize the distribution of both features before and after scaling. We’ll use the `ggplot2` package for this:

``````library(ggplot2)
library(dplyr)
library(tidyr)

# Make Scaled data and cbind to original
scaled_data <- scale(data)
setNames(cbind(data, scaled_data), c("height", "weight", "height_scaled", "weight_scaled")) -> data

# Tidy data for facet plotting
data_long <- pivot_longer(
data,
cols = c(height, weight, height_scaled, weight_scaled),
names_to = "variable",
values_to = "value"
)

# Visualize
data_long |>
ggplot(aes(x = value, fill = variable)) +
geom_histogram(
bins = 30,
alpha = 0.328) +
facet_wrap(~variable, scales = "free") +
labs(
title = "Distribution of Height and Weight Before and After Scaling"
) +
theme_minimal()``````

Run this code and see the magic! The histograms before scaling will show a clear difference in spread between height and weight. After scaling, both distributions will have a similar shape, centered around 0 with a standard deviation of 1.

# Try it Yourself!

This is just a basic example. Get your hands dirty! Try scaling data from your own projects and see how it affects your analysis. Remember, scaling is just one step in data pre-processing. Explore other techniques like centering or normalization depending on your specific needs.

So, the next time you have features with different scales, consider using `scale()` to bring them to a level playing field and unlock the full potential of your models!