Alternative of by statement in Proc IML

[Rasheed]

Ok I try

I would be grateful if you could pleas tell how could I save each matrix in different variable I am using following program

r = 1:2;  /* row numbers to extract from x */

do boot = 1 to 2;

  y = x[r, 2:3];

  < do stuff here with the 2x2 matrix y >

  r = r + 2;  /* increment row numbers for next boot */

end;

Plz help me in this regard

[IanWakeling]

If you are prepared to sacrifice readability of code, then you can create a character matrix y that contains the names of each matrix in your list. Then you can use the VALUE() function and the VALSET() call every time you want to refer to those matrices.

  x = {
1 0.0036813 0.0030405 ,
1 0.0030405 0.0032935 ,
2 0.0015928 0.0017098 ,
2 0.0017098 0.0020805 };

  y = 'y_1' : 'y_2';  /* define matrix NAMES */

  r = 1:2;
  do k = 1 to 2;
    call valset( y, x[r, 2:3]);      /* create the matrix y_k */
    print (value( y ));              /* print y_k */
    call valset( y, value(y)#2 ); /* multiply by 2 */
    print (value( y ));              /* print again */
    r = r + 2;
  end;

I can see Rick's point that it will be easier to store all the results in once place, however I would prefer to have a choice and for there to be an easier way to create a list of matrices, where each element can be a matrix of any size.

[Rasheed]

Thanks Ian I used your code it worked fine for me thank you again Now one thing is more I want to convert these separated matrices into separate data sets and using following command but not working pls guide. Here I want to convert matrices C_1, C_2 into data sets CD_1 CD_2

do k = 1 to 2;

call execute('create ' + CD +'  from value( C);');                                                                                                                                                                                                 

append from  value(C);                                                                                                                                                                                                                                         

call execute('close ' + CD + ';' );

end;

[IanWakeling]

In this context (CREATE and APPEND), you do not want the value of the matrix, just its name.  So you would need to modify the code as follows:

do k = 1 to 2;

  call execute('create ' + CD +'  from ' + C + ';');

  call execute('append from ' + C + ';') ;

  call execute('close ' + CD + ';' );

end;

and because of the call execute, you would have to use this code within a module.  Be warned this could get messy if you are creating hundreds of data sets,  why not save the original matrix from the beginning of this thread as a SAS data set?

[Rasheed]

Thanks again Ian, is there any option from which we can convert into data sets without using module?

[IanWakeling]

You would have to copy your matrix C to another matrix for each iteration of the loop, as there is no facility to supply an expression for the 'matrix name' that follows the keyword FROM.   For example:

do k = 1 to 2;

  z = value(C);

  create (CD) from z;

  append from z ;

  close (CD);

end;

[Rasheed]

When I run the above previous code I got the following error

do k = 1 to 2;

891

892    z = value(C);

893

894    create (CD) from z;

              -

              22

              76

ERROR 22-322: Expecting a name.

ERROR 76-322: Syntax error, statement will be ignored.

895

896    append from z ;

897

898    close (CD);

             -

             22

             200

ERROR 22-322: Syntax error, expecting one of the following: a name, ;.

ERROR 200-322: The symbol is not recognized and will be ignored.

899

900    end;

ERROR: END does not occur within DO group at line=900 col=3.

[IanWakeling]

I presume you have CD defined with something like:

CD='CD_1':'CD_2';

In which case it might be a version thing as it is working for me in SAS/IML 13.1.  Perhaps Rick could confirm this, and also comment on why an expression was allowed for the data set name, but not for the matrix name.

[Rasheed]

There are two matrices C_1 and C_2 and I am using following code without module to convert them in to data sets CD_1 and CD_2

CD='CD_1':'CD_2';

do k = 1 to 2;

  z = value(C);

  create (CD) from z;

  append from z ;

  close (CD);

end;

But still got the same error

[Rick_SAS]

Reading and writing data sets whose names are contained in a character matrix is supported beginning in  SAS/IML 12.1 (released with 9.3m2). See http://blogs.sas.com/content/iml/2013/07/29/read-data-sets-array-names.html

Ian: The APPEND statement doesn't support expressions because it is valid syntax to specify a character matrix, in which case the APPEND statement writes that data to the data set.

[Rick_SAS]

If you wish to pursue Ian's suggestion, there is more information about VALUE and VALSET in the article "Indirect assignment: How to create and use matrices named x1, x2,..., xn"