# Understanding Histograms and Kernel Density Estimation | by Reza Bagheri | Dec, 2023

A histogram is a graph that visualizes the frequency of numerical information. It’s generally utilized in information science and statistics to have a uncooked estimate of the distribution of a dataset. Kernel density estimation (KDE) is a technique for estimating the chance density perform (PDF) of a random variable with an unknown distribution utilizing a random pattern drawn from that distribution. Therefore, it permits us to deduce the chance density of a inhabitants, based mostly on a finite dataset sampled from it. KDE is commonly utilized in sign processing and information science, as a necessary device to estimate the chance density. This text discusses the mathematics and instinct behind histograms and KDE and their benefits and limitations. It additionally demonstrates how KDE may be carried out in Python from scratch. *All figures on this article had been created by the creator.*

**Likelihood density perform**

Let *X* be a steady random variable. The chance that *X* takes a price within the interval [a, b] may be written as

the place *f(x)* is *X*‘s chance density perform (PDF). The *cumulative density perform* (CDF) of *X* is outlined as:

Therefore the CDF of *X*, evaluated at *x*, is the chance that *X* will take a price lower than or equal to *x*. Utilizing Equation 1, we will write:

Utilizing the basic theorem of calculus, we will present that

which signifies that the PDF of *X* may be decided by taking the by-product of its CDF with respect to *x*. A histogram is the best strategy to estimate the PDF of a dataset, and as we present within the subsequent part it makes use of Equation 1 for this goal.

**Histograms**

In Itemizing 1, we create a bimodal distribution as a mix of two regular distributions and draw a random pattern of measurement 1000 from this distribution. Right here we combine two regular distributions:

Therefore, the imply of the conventional distributions is 0 and 4 respectively and their variance is 1 and 0.8 respectively. The blending coefficients are 0.7 and 0.3, so the PDF of the combination of those distributions is:

Itemizing 1 plots this PDF and pattern in Determine 1.