topic Re: one index function question in SAS Programming

one index function question

Niugg2010 — Mon, 03 Oct 2016 03:03:07 GMT

X=”GTTCACTAGCAACCTCAAACAGACACCATGGTGCACCTG”

a=”-CCTCA”

b=”A-CTCA”

c=”AC-TCA”

d=”ACC-CA”

e=”ACCT-A”

f=”ACCTC-”

“-“ is any one letter, such as “G” “T” or “A”;

I thought a,b,c,d,e,f are all equal to pattern “ACCTCA”

How can I write an index function to find the position of a (or b, or c, or d, or e, or f) in X;

Thanks.

Re: one index function question

LaurieF — Mon, 03 Oct 2016 04:02:04 GMT

I'm no great Perl maven, but using prxmatch will give you what you're after. Here's how I did it:

data _null_;
infile cards;
retain x "GTTCACTAGCAACCTCAAACAGACACCATGGTGCACCTG";
length pattern $ 9;
input pattern;
match = prxmatch('/' || strip(pattern) || '/', x);
put match=;
cards;
.CCTCA
A.CTCA
AC.TCA
ACC.CA
ACCT.A
ACCTC.
;
run;

In Perl, the wild card is '.', not '-'.

When this code is run, the pattern is found at position 12 every time. If it weren't found, like with index, it would return 0.

Re: one index function question

Patrick — Mon, 03 Oct 2016 04:07:33 GMT

find() or index() don't allow for wildcard searches.

You could either use a Regular Expression or a Like operator in a where clause.

Would you just need the first position where one of your patterns matches? And would ALL patterns have to match or only one of them?

Re: one index function question

Reeza — Mon, 03 Oct 2016 04:49:29 GMT

Also, look into COMPGED, Complev and other functions.

Not sure they'll give you enough control though.

Re: one index function question

Niugg2010 — Mon, 03 Oct 2016 10:34:13 GMT

Thanks a lot. I never used prxmatch function. I will try it.

Re: one index function question

Niugg2010 — Mon, 03 Oct 2016 10:53:06 GMT

X=”GTTCACTAGCAACCTCAAACAGACACCATGGTGCACCTG”
pattern="ACCTCA" or pattern="A-CTCA"

Actually I want to check " if X contains pattern ";
I found I can not use this logistic judgement,

So I thought maybe I can use index() function,

if result >0 it means X contains pattern;

if result =0 it means X does not contains pattern.

if someone can suggest a better method, it will be great.

Re: one index function question

Patrick — Mon, 03 Oct 2016 11:04:27 GMT

You say "pattern" I think RegEx. Below a variation of what has already been proposed.

data sample;
  input string:$60.;
  match_pos= prxmatch('/(.CCTCA|A.CTCA|AC.TCA|ACC.CA|ACCT.A|ACCTC.)/oi',string);
  match_flg= prxmatch('/(.CCTCA|A.CTCA|AC.TCA|ACC.CA|ACCT.A|ACCTC.)/oi',string)>0;
  datalines;
GTTCACTAGCAACCTCAAACAGACACCATGGTGCACCTG
GTTCACTAGCACACTCAAACAGACACCATGGTGCACCTG
;
run;

Re: one index function question

Niugg2010 — Mon, 03 Oct 2016 13:11:59 GMT

Thanks a lot. It is very helpful.