The following code will plot the close series data:

plot(close)

However, I want to normalize the close series by today’s close value:

// If the today's (latest) close is 165, we will divide the close series by 165.
plot(close/165)

This will give us a normalized series where the latest normalized value will be 1, and we can compare different securities together (forward comparison).

The latest close varies every day. How could I normalize the close series by today’s close value?

The following code is not correct:

// close[0] mean the close data on the drawing bar, not today's close (latest close)
plot(close/close[0])