I tried with the following code without success, sorry I'm a newbie:

#define N 10 // Number of bars

function run()
{

var myClose[10] = { 1,3,9,4,12,6,5,10,15,5};
var LR_line[10];

// variables
var a,b,c,sumy=0.0,sumx=0.0,sumxy=0.0,sumx2=0.0,h=0.0,l=0.0;
int x,i;
int barsToCount=50;


for( i=0; i<N; i++)
{
sumy+=myClose[i];
sumxy+=myClose[i]*i;
sumx+=i;
sumx2+=i*i;
}

c=sumx2*N-sumx*sumx;

// Line equation
b=(sumxy*barsToCount-sumx*sumy)/c;
a=(sumy-sumx*b)/N;

for(x=0;x<N;x++)
{ LR_line[x]=a+b*x;
plot("NEW_linreg", LR_line[x],MAIN, RED);
}




}

The calculation should be correct; the issue is related how to plot the straight line in a time chart.