# NumPy Histograms

So far, you’ve been working with what could best be called **frequency tables**. But mathematically, a histogram is a mapping of bins (intervals) to frequencies. More technically, it can be used to approximate the **probability density function** (PDF) of the underlying variable.

A true histogram first **bins** the range of values and then counts the number of values that fall into each bin. This is what NumPy’s `histogram()`

does, and it’s the basis for other functions you’ll see here later in Python libraries such as Matplotlib and Pandas.

Consider a sample of floats drawn from the Laplace distribution. This distribution has fatter tails than a normal distribution and has two descriptive parameters (location and scale):

```
>>> import numpy as np
>>> # `numpy.random` uses its own PRNG.
>>> np.random.seed(444)
>>> np.set_printoptions(precision=3)
>>> d = np.random.laplace(loc=15, scale=3, size=500)
>>> d[:5]
array([18.406, 18.087, 16.004, 16.221, 7.358])
```

In this case, you’re working with a continuous distribution, and it wouldn’t be very helpful to tally each float independently, down to the umpteenth decimal place. Instead, you can bin or **bucket** the data and count the observations that fall into each bin. The histogram is the resulting count of values within each bin.

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