Technical indicators can be computerized directly using the ta library under Pine Script.

To calculate the Moving Average (MA) on closing prices, we use the following instruction (for an MA10):

To plot this indicator with a red curve, we use the function plot:

=> 

Plot of the Moving Average (MA) in red color

For the 14-period RSI:

To obtain the average, and upper/lower bands of the Bollinger Bands over 20 periods with a standard deviation of 1:

We may also want to calculate the high points on the last candles. Eg. here the calculation of the highest over the last 20 candles:

To obtain all the technical indicators available with the ta library, type ta. and the list of indicators will then be displayed (scroll with the up/down arrows on the keyboard):