Set the First Trading Bar Values to Not a Number

The "SetNaN" function updates the first N-values of a time-series and replaces them with "NaN" (Not a number).
A "NaN" value is not drawn on a chart and it always return false when used in a trading rule.
For example, let us create a "NaN" array:
a = ref(close, 10000000000);

In a trading chart, when you apply the "Plot" function to this array, nothing is displayed.

If you backtest the following rule:
buy = a > 0 or a <= 0;
It will always return "0" (no signals).


Examples of use for the "SetNaN" function:

- Ignore the first N-Bars

While developing a trading system, if you want to avoid entering new positions for the first 100-bars of a stock or security, type:

buy = SetNaN(buy, 100);

- Support/Resistance Range

Using the "AutoSR" function, you can plot support and resistance lines on a chart.

To plot a short-term support:

a = AutoSR(0, 0, 50);
plot(a, "");

This line is drawn for all bars (even the ones that occurred before the last 50 bars).

To fix this and draw the support line for the last 50 bars only, type:

a = AutoSR(0, 0, 50);
a = SetNaN(a, TotalBars() - 50);
plot(a, "");

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