StDev ( int length);

Default values:

length: 12


Returns the standard deviation of data for the last length bars.

General Information

Standard deviation measures how widely values range from the average value. Standard deviation is calculated as a square root of variance, which is the average of the squared deviations from the mean.


Input parameters

Parameter Default value Description
data - Defines the variable for which the standard deviation is calculated.
length 12 Defines the period on which the standard deviation is calculated.


script StDevTS {

input data = close;
input length = 12;
def avgData = Average(data, length);
plot StDevTS1 = Sqrt( (fold i = 0 to length with SD do SD + Sqr(GetValue(data, i) - avgData) ) / length);
plot StDevTS2 = Sqrt(Average(Sqr(data), length) - Sqr(Average(data, length)));

declare lower;
input length = 10;
plot StDev1 = StDev(close, length);
plot StDev2 = StDevTS(close, length).StDevTS1;
plot StDev3 = StDevTS(close, length).StDevTS2;

The code draws three plots that show the standard deviation for the close price of the current symbol on the defined period. The StDev1 plot is based on the built-in function, the StDev2 and StDev3 plots are based on its thinkScript® implementation, using two different mechanisms of calculation. All the three plots coincide, forming a single plot.