[R] Chars as numbers

[Josef Eschgfaeller]

> as.numeric

Some weeks ago one discussed on the list about how
to transform a hexadecimal representation to
decimal digits. Specifically one has to transform
'a' to 10 etc. In C one does this with 'a'-87,
but I did not find a function for this in R.
Using match on letterdigits as in the following
is of course a little slow when repeated often.
---------------------------------------
Hex = function (rep16)
{rep16=tolower(rep16)
u=strsplit(rep16,'',perl=T)[[1]]
letterdigits=c(0:9,letters)
v=sapply(u,function (x)
   match(x,letterdigits)-1)
v=as.numeric(v)
Horner(v,16)}

Horner = function (v,alfa=2)
{b=v[1]; m=length(v)
if (m>1) for (i in 2:m)
b=b*alfa+v[i]; b}

# Example:
for (x in c('0','a0','10e','f0ae'))
print(Hex(x))
# 0
# 160
# 270
# 61614
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Josef Eschgfäller

-- 
Josef Eschgfäller
Dipartimento Matematico
Universita' di Ferrara
http://felix.unife.it