Hey there! Let's break down these two parameters—they both control your histogram's bins, but operate in distinct ways, so it's easy to mix them up at first.

What's nclass? #

nclass is a quick shortcut to suggest the approximate number of bins you want for your histogram. Here's the lowdown:

• When you use hist(b, nclass=10), you're telling R: "I want around 10 bins for my data b."
• R doesn't just split your data into exactly 10 equal chunks—it calculates a set of break points (bin edges) using a formula that aims to get as close to 10 bins as possible, while keeping the bins mathematically sensible for your data's range and distribution. The final number of bins might be slightly more or less than 10, depending on your data.
• This is perfect when you have a rough idea of how granular you want your histogram to be, and don't want to dive into defining exact bin edges.

What's breaks? #

breaks is the more flexible, powerful parameter for controlling binning. It can accept several types of inputs to define exactly how your bins are set up:

1. A single number (e.g., breaks=10) #

• Similar to nclass, this tells R to aim for around 10 bins—but it uses a different default algorithm (Sturges' rule, by default) to calculate the break points. The end result might be close to nclass=10, but the underlying math to get there is different.

2. A vector of exact break points #

• If you want full control, pass a vector like breaks=c(0, 2, 4, 6, 8, 10). This forces the histogram to use these exact edges, creating bins for 0-2, 2-4, etc.—no guesswork involved.

3. A named binning method #

• You can pass strings like "FD" (Freedman-Diaconis rule) or "scott", which are statistical methods that calculate the optimal number of bins based on your data's spread and sample size. This is great when you want R to pick the best bin count for your specific dataset.

Key Difference to Remember #

• Use nclass for a fast, rough bin count when you don't need precision.
• Use breaks when you need exact control over bin edges, or want to use a specific statistical method to determine binning.

内容的提问来源于stack exchange，提问作者user18253267