\\ 20894 Menezes/, 182.
t_autocorr (v,d) = {my (s=0,n=#v);
for (i=1,n-d,s+=(v[i]!=v[i+d])); s}

t_erf (x) = 1-erfc(x)

\\ Frequencies of elements in vector v.
t_frequencies (v) = {my (el,h,A,i);
el=[]; h=[]; for (j=1,#v, x=v[j];
if (i=t_pos(x,el),h[i]++,\
el=concat(el,[x]); h=concat(h,[1])));
A=matrix(#el,2,i,j,if(j==1,el[i],h[i]));
vecsort(A~,2,4)}

\\ Maximum of forward partial |sums|.
t_maxsum (v) = {my (s=0,m=0);
for (i=1,#v, s+=v[i]; sa=abs(s); if (sa>m,m=sa)); m}

\\ If necessary, add 0.0 for obtaining a real number.
t_mean (v) = vecsum(v)/#v

\\ If necessary, add 0.0 for obtaining a real number.
t_median (v) = {my (n);
v=vecsort(v); n=#v; if (n%2,v[n\2+1],(v[n/2]+v[n/2+1])/2)}

\\ N(0,1).
t_Phi (x) = 0.5*(1+t_erf(x/sqrt(2)))