Beginner tutorial : Linear Regression in R

Linear regression is a common technique used to show relationship between a predictor and outcome. For example, say you are trying to predict a car acceleration (0 to 100  km) based on its engine house power.

You might have a sample data shown below

Car horse power       Acceleration per second

100                            120
110                            150
120                            160
150                            170
200                              x

Given a car horse power 200 what would its acceleration (value x) be?

Linear regression takes a straight line that pass through certain points. It can represented with the following equation

y = ax + b

Lets use R to help us with prediction

Line #5, we can see that we are using R method called lm to create our model.

lm(y ~ x) means y is a predicted by using x term. In our case, Y is acceleration per second. X is our horse power.

Let try to predict using our model above.

As you can see, given a 200 house power engine, we can have 5 second acceleration 0 to 100 km/h.

Some other terms might be of interested

a) R square - is a measure of how close prediction fits on regression line.  0% means regression line is not relevant at all. 100% means Y can be explained by the line.

b) F statistic - in regression F statistic is used to compare how best a model fits into dataset.


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