topic Re: Reading data from text-file into array in SAS Programming

Reading data from text-file into array

Hedegaard — Wed, 04 Apr 2012 11:26:49 GMT

Hi,

I have a text file containing 20 x 20 numbers, which are all of two digits. I am trying to read these numbers into a 20 x 20 array (which I call "a"). When I put the array a in my code below, I don't get a 20 x 20 array, but something enormous, which looks more like each entry a[i,j] of the array contains 20 entries by itself. Can anyone see where I went wrong?

Kind regards,

Hedegaard.

proc import datafile = "C:\Documents and Settings\Desktop\grid.txt" out=work.griddata replace;

     delimiter = " ";
     getnames = no;
     guessingrows = 20;
run;

data grid;
set griddata;

array var{1:20} VAR1-VAR20;
array a{20,20};

do i = 1 to 20;
a[i,_N_] = var;
end;

put a

;

run;

Reading data from text-file into array

manojinpec — Wed, 04 Apr 2012 11:32:31 GMT

Can please send the dummy text file which you are trying to read?

Re: Reading data from text-file into array

Hedegaard — Wed, 04 Apr 2012 11:37:45 GMT

Hello,

I have attached the file.

Re: Reading data from text-file into array

Haikuo — Wed, 04 Apr 2012 12:08:15 GMT

two-dimention arrays is denoted as array(row, column). So for your purpose, it will be easier to read if you define your array:

a[_n_,i] = var;

instead of a[i,_N_] = var;

Other than that, I don't see any problems, it works the way it should. Both will give you 400 new variables, so I don't understand your question. You probably was looking for something proc iml does, but not arrays.

Regards,

Haikuo

Re: Reading data from text-file into array

Hedegaard — Wed, 04 Apr 2012 12:39:35 GMT

Hm, I think I understand now.

What bothered me was that there seemed to be a 20 rows of each entry of the array a, so that when I asked SAS to "put a[i,j];" for some specific choice of i and j, then I'd see a 20 entry long list in the log, where all but one entry was missing. This might be because it creates the array for each of the twenty rows in the input file?

I am interested in working with the final and filled up array, so I suppose I could encapsule whatever I want to do with the array in an "if _N_=20" condition.

Edit: And it would appear I also need to add a "retain" statement.

Re: Reading data from text-file into array

Haikuo — Wed, 04 Apr 2012 12:52:18 GMT

Hm, in that case, you could try the following, it may meet your need?

data grid;

infile "C:\Documents and Settings\Desktop\grid.txt";

array a{20,20};

do i = 1 to 20;

do j=1 to 20;

input a[i,j] @@;

end;

put a

;

run;

Haikuo

Re: Reading data from text-file into array

Hedegaard — Wed, 04 Apr 2012 13:23:12 GMT

Hai.kuo, that works perfectly!

I'm not sure why though? What does the input command do exactly?

Re: Reading data from text-file into array

Haikuo — Wed, 04 Apr 2012 13:34:32 GMT

Cause you need 400 variables in ONE line populated with values. If you already have them in a dataset of 20 lines (rows, obs), it will be a lot harder to achieve your goal. 'input @@' will let you keep reading until the end of the file, which can be considered as just one line if numer of your variables are equal or more than the number of the data elements in your raw flat file.

Haikuo

Re: Reading data from text-file into array

Tal — Sat, 13 Oct 2012 22:24:23 GMT

hey Haikuo,

Re: Reading data from text-file into array

art297 — Sat, 13 Oct 2012 22:51:02 GMT

Your put statement is after your two loops, thus i=21 and j=21. Therefore, when the system confronts:

put a(i,j);

It is being asked for an array value that is outside of the parameters you declared.

Re: Reading data from text-file into array

Tal — Sat, 13 Oct 2012 23:13:33 GMT

Thanks Arthur.

After changing the 20 to 19 SAS did not give me any errors but when i have put out of the loop SAS does not write the observations onto the log window.Why?

Re: Reading data from text-file into array

art297 — Sun, 14 Oct 2012 14:57:13 GMT

Not sure what you did or why. With a 20 by 20 matrix you have 400 values. By having a put statement within the loop it is being addressed 400 times thus outputting 400 values.

When you move it outside of the loop it is only outputting 1 value. Why did you move it outside of the loop in the first place?

Re: Reading data from text-file into array

Tal — Mon, 15 Oct 2012 02:14:37 GMT

thanks Arthur.

With PUT inside the loop,SAS is writing 400x1 observations in the log and i kinda wanted to see something like a matrix form of results so i thought if i play with PUT would eventually get that result lol but i guess when it is out SAS only writes the last element of the array.

Re: Reading data from text-file into array

art297 — Mon, 15 Oct 2012 13:52:22 GMT

How about?:

data grid;

infile "C:\Documents and Settings\Desktop\grid.txt";

array a{20,20};

do i = 1 to 20;

do j=1 to 20;

input a[i,j] @@;

if j lt 20 then put @(j*4) a[i,j] @;

else put a[i,j];

end;

run;

Re: Reading data from text-file into array

Ksharp — Tue, 16 Oct 2012 04:56:24 GMT

I think the array you mentioned is temporary array not normal variable array.

data _null_;
infile 'c:\grid.txt' end=last;
array a{20,20} _temporary_;
array x{20} x1-x20;
input x1-x20;
do k=1 to 20;
a{_n_,k}=x{k};
end;




if last then do;
do i=1 to 20;
 do j=1 to 20;
  put a{i,j} @ ;
 end;
 put / ;
end;
end;
run;

Ksharp

Re: Reading data from text-file into array

Tal — Sun, 21 Oct 2012 21:21:14 GMT

thanks both

Re: Reading data from text-file into array

Tal — Sun, 21 Oct 2012 21:24:56 GMT

thanks Arthur