SAS Companion for the OS/2 Environment

DDE Examples

This section provides several examples of using DDE with the SAS System under OS/2. These examples use Microsoft Excel as the DDE server, but any application that supports DDE as a server can communicate with the SAS System. Before you run most of these examples, you must first invoke the server application and open the spreadsheet used in the example. The only exception to this requirement is found in the example shown in Using DDE and the SYSTEM Topic to Execute Commands in an Application. In this later example, you should not invoke Excel first because the example program invokes Excel for you.

If you did not start Excel before you began your SAS session, you can turn off the XWAIT and XSYNC options and use the X statement to start Excel, as in the following example:

options noxwait noxsync;
x 'excel'; /* you might need to specify */
           /* the complete pathname     */

Note: DDE examples are included in the host-specific sample programs that you can access from the Help menu. [cautend]

Using DDE to Write Data

Suppose you want to send data from a SAS session to an Excel spreadsheet. You want to use rows 1 through 100 and columns 1 through 3. To do this, submit the following program:

/* The DDE link is established using   */
/* Microsoft Excel SHEET1, rows 1      */
/* through 100 and columns 1 through 3 */
filename random dde
   'excel¦sheet1!r1c1:r100c3';
data random;
   file random;
   do i=1 to 100;
      x=ranuni(i);
      y=10+x;
      z=x-10;
      put x y z;
   end;
run;

Using DDE to Read Data

You can also use DDE to read data from an Excel application into the SAS System, as in the following example:

/* The DDE link is established using   */
/* Microsoft Excel SHEET1, rows 1      */
/* through 10 and columns 1 through 3  */
filename monthly
  dde 'excel¦sheet1!r1c1:r10c3';
data monthly;
   infile monthly;
   input var1 var2 var3;
run;
proc print;
run;

Using DDE and the SYSTEM Topic to Execute Commands in an Application

You can issue commands to Excel or other DDE-compatible programs directly from the SAS System using DDE. In the following example, the Excel application is invoked; a spreadsheet called SHEET1 is loaded; data are sent from the SAS System to Excel for row 1, column 1 to row 20, column 3; and the commands required to select a data range and sort the data are issued. The spreadsheet is then saved, and the Excel application is terminated.

/* This code assumes that Excel       */
/* is installed on the current        */
/* drive in a directory called EXCEL. */
options noxwait noxsync;
x 'excel';  /* you might need to specify */
            /* the entire pathname       */
/* Sleep for 60 seconds to give */
/* Excel time to come up.       */
data _null_;
   x=sleep(60);
run;
/* The DDE link is established using   */
/* Microsoft Excel SHEET1, rows 1      */
/* through 20 and columns 1 through 3  */
filename data
   dde 'excel¦sheet1!r1c1:r20c3';
data one;
   file data;
   do i=1 to 20;
      x=ranuni(i);
      y=x+10;
      z=x/2;
      put x y z;
   end;
run;
/* Microsoft defines the DDE topic */
/* SYSTEM to enable commands to be */
/* executed within Excel.          */
filename cmds dde 'excel¦system';
/* These PUT statements are       */
/* executing Excel macro commands */
data _null_;
   file cmds;
   put '[SELECT("R1C1:R20C3")]';
   put '[SORT(1,"R1C1",1)]';
   put '[SAVE()]';
   put '[QUIT()]';
run;

Using the NOTAB Option with DDE

The SAS System expects to see a TAB character placed between each variable that is communicated across the DDE link. Similarly, the SAS System places a TAB character between variables when data are transmitted across the link. When you use the NOTAB option in a FILENAME statement that uses the DDE device-type keyword, the SAS System accepts character delimiters other than tabs between variables.

The NOTAB option also can be used to store full character strings, including embedded blanks, in a single spreadsheet cell. For example, if a link is established between the SAS System and the Excel application, and if a SAS variable contains a character string with embedded blanks, each word of the character string is normally stored in a single cell. To store the entire string including embedded blanks in a single cell, use the NOTAB option as in the following example:

/* Without the NOTAB option, column1  */
/* contains 'test' and column2        */
/* contains 'one'.                    */
filename test
  dde 'excel¦sheet1!r1c1:r1c2';
data string;
   file test;
   a='test one';
   b='test two';
   put a $15. b $15.;
run;
/* You can use the NOTAB option to store  */
/* each variable in a separate cell. To   */
/* do this, you must force a tab          */
/* ('09'x) between each variable, as in   */
/* the PUT statement.                     */
/* After this DATA step executes, column1 */
/* contains 'test one' and column2        */
/* contains 'test two'.                   */
filename test
  dde 'excel¦sheet1!r2c1:r2c2' notab;
data string;
   file test;
   a='test one';
   b='test two';
   put a $15. '09'x b $15.;
run;

Using the DDE HOTLINK

If the HOTLINK option is specified, the DDE link is activated every time the data in the specified spreadsheet range are updated. In addition, DDE enables you to poll the data when the HOTLINK option is specified to determine whether data within the range that was specified have been changed. If no data have changed, the HOTLINK option returns a record of 0 bytes. In the following example, row 1, column 1 of the spreadsheet SHEET1 contains the daily production total. Every time the value in this cell changes, the SAS System reads in the new value and outputs the observation to a data set. In this example, a second cell in row 5, column 1 is defined as a status field. Once the user completes data entry, typing any character in this field terminates the DDE link:

/* Enter data into Excel SHEET1 in   */
/* row 1 column 1. When you          */
/* are through entering data, place  */
/* any character in row 5            */
/* column 1, and the DDE link is     */
/* terminated.                       */
filename daily
  dde 'excel¦sheet1!r1c1' hotlink;
filename status
  dde 'excel¦sheet1!r5c1' hotlink;
data daily;
   infile status length=flag;
   input @;
   if flag ne 0 then stop;
   infile daily length=b;
   input @;
   /* If data have changed, then the */
   /* incoming record length         */
   /* is not equal to 0.             */
   if b ne 0 then
      do;
         input total $;
         put total=;
         output;
      end;
run;

It is possible to establish multiple DDE sessions. The previous example uses two separate DDE links. When the HOTLINK option is used and there are multiple cells referenced in the item specification, if any one of the cells changes, then all cells are transmitted.

Unless the HOTLINK option is specified, DDE is performed as a single one-time data transfer. That is, the values currently stored in the spreadsheet cells at the time that the DDE is processed are values that are transferred.

Using the !DDE_FLUSH String to Transfer Data Dynamically

DDE also enables you to program when the DDE buffer is dumped during a DDE link. Normally, the data in the DDE buffer are transmitted when the DDE link is closed at the end of the DATA step. However, the special string '!DDE_FLUSH' issued in a PUT statement instructs the SAS System to dump the contents of the DDE buffer. This function gives you considerable flexibility in the way DDE is used, including the capacity to transfer data dynamically through the DATA step, as in the following example:

/* A DATA step window is displayed.   */
/* Enter data as prompted.            */
/* When you are finished, enter STOP  */
/* on the command line.               */
filename entry
   dde 'excel¦sheet1!r1c1:r1c3';
dm 'pmenu off';
data entry;
   if _n_=1 then
      do;
         window ENTRY color=black
         #3 'This is data for Row 1 Column 1'
            c=cyan +2 var1 $10. c=orange
         #5 'This is data for Row 1 Column 2'
            c=cyan +2 var2 $10. c=orange
         #7 'This is data for Row 1 Column 3'
            c=cyan +2 var3 $10. c=orange;
      end;
   flsh='!DDE_FLUSH';
   file entry;
   do while (upcase(_cmd_) ne 'STOP');
      display entry;
      put var1 var2 var3 flsh;
      output;
      VAR1='';
      VAR2='';
      VAR3='';
   end;
   stop;
run;
dm 'pmenu on';

Reading Missing Data

This example illustrates reading missing data from an Excel spreadsheet called SHEET1. This example reads the data in columns 1 through 3 and rows 10 through 20. Some of the data cells may be blank. Here is an example of what some of the data look like:

...
10   John    Raleigh      Cardinals
11   Jose    North Bend   Orioles
12   Kurt    Yelm         Red Sox
13   Brent                Dodgers
...

Following is the code that can read these data correctly into a SAS data set:

filename mydata
  dde 'excel¦sheet1!r10c1:r20c3';
data in;
   infile mydata dlm='09'x notab
          dsd missover;
   informat name $10. town $char20.
            team $char20.;
   input name town team;
run;
proc print data=in;
run;

In this example, the NOTAB option tells the SAS System not to convert tabs that are sent from the Excel application into blanks. Therefore, the TAB character can be used as the delimiter between data values. The DLM= option specifies the delimiter character, and '09'x is the hexadecimal representation of the TAB character. The DSD option specifies that two consecutive delimiters should represent a missing value. The default delimiter is a comma. For more information, see the DSD option in SAS Language Reference: Dictionary. The MISSOVER option prevents a SAS program from going to a new input line if it does not find values in the current line for all the INPUT statement variables. With the MISSOVER option, when an INPUT statement reaches the end of the current record, values that are expected but not found are set to missing.

The INFORMAT statement forces the DATA step to use modified list input, which is crucial to this example. If you do not use modified list input, you receive incorrect results. The necessity of using modified list input is not DDE specific; you would need it even if you were using data in a CARDS statement, whether your data were delimited by blanks or commas.

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