Do While Loop Not executing

[jcdataguy]

Hi experts!  I need help with this while loop. Can u tell visually what is wrong with it? It should iterate through two arrays (flow_field and bal_field) and loop while "switch_in" is more than zero:

data do_until;
set money_table;

array flow_field [*]  _from_1  _from_2  _from_3   _from_4  _from_5 ;
array bal_field [*]   bal_1 bal_2 bal_3  bal_4  bal_5 ;

switch_in = 100000;

do while (switch_in > 0);
  do i=1 to 5;
     if bal_field[i] lt 0 and bal_field[i] ne . then do;
         flow_field[i] = min(switch_in, abs(bal_field[i]));
        switch_in = switch_in - (abs(bal_field[i]));
      end;
  end;
end;
run;

[SASKiwi · Accepted solution]

Looks like you are expecting switch_in to increment between rows. You need to add a RETAIN statement to make this happen (position is not important):

retain switch_in;

[jcdataguy]

Thanks for your reply @SASKiwi .  But I want Switch_In to decrease with each passing of teh loop until it reaches 0. It loop it's supposed to iterate for those bal_flow that are less than 0. 

[jcdataguy]

HERE IS SOME SAMPLE DATA:

The total values in the _from fields cannot exceed the switch_in values

[SASKiwi]

@jcdataguy - An increment can be either positive or negative but you will still need the RETAIN for it to work.

[Astounding]

One possibility (at least in theory):  Once you hit an observation that has all non-negative balance fields, the logic fails to change switch_in.  The program becomes an infinite loop.

[Patrick]

If for a specific row below condition is never true....

if bal_field[i] lt 0 and bal_field[i] ne . then

...then the value for switch_in never changes but remains 100000 which results in an infinite loop.

Here some code to test this using the sample data you've posted.

DATA money_table;
  LENGTH
    BAL_1              8
    BAL_2              8
    BAL_3              8
    BAL_4              8
    BAL_5              8
    total_netbal       8
    _FROM_1            8
    FROM_2             8
    _FROM_3            8
    FROM_4             8
    _FROM_5            8
    SWITCH_IN          8;
  FORMAT
    BAL_1            DOLLAR19.1
    BAL_2            DOLLAR19.1
    BAL_3            DOLLAR19.1
    BAL_4            DOLLAR19.1
    BAL_5            DOLLAR16.2
    total_netbal     DOLLAR19.1
    _FROM_1          DOLLAR19.1
    FROM_2           DOLLAR19.1
    _FROM_3          DOLLAR19.1
    FROM_4           DOLLAR19.1
    _FROM_5          DOLLAR19.1
    SWITCH_IN        BEST12.;
  INFORMAT
    BAL_1            DOLLAR19.
    BAL_2            DOLLAR19.
    BAL_3            DOLLAR19.
    BAL_4            DOLLAR19.
    BAL_5            DOLLAR16.
    total_netbal     DOLLAR19.
    _FROM_1          DOLLAR19.
    FROM_2           DOLLAR19.
    _FROM_3          DOLLAR19.
    FROM_4           DOLLAR19.
    _FROM_5          DOLLAR19.
    SWITCH_IN        BEST12.;
  INFILE DATALINES4
    DLM='7F'x
    MISSOVER
    DSD;
  INPUT
    BAL_1            : BEST32.
    BAL_2            : BEST32.
    BAL_3            : BEST32.
    BAL_4            : BEST32.
    BAL_5            : DOLLAR19.
    total_netbal     : BEST32.
    _FROM_1          : BEST32.
    FROM_2           : BEST32.
    _FROM_3          : BEST32.
    FROM_4           : BEST32.
    _FROM_5          : BEST32.
    SWITCH_IN        : BEST32.;
  DATALINES4;
542.5958829.64288.119999999999. 59660.3558829.640...5000
899.470.. 899.4700...10000
1285.2579059.13-4543.95. 75800.4375800.433258.70000000001003258.7000000000115000
-61360.7152471.48.. 91110.7891110.7861360.761360.70020000
8021.2157220.79.34.1599999999999 65276.1657220.790...25000
-15165.2540021.09.. 24855.8424855.8415165.2515165.250030000
141.0438611.91-882.77. 37870.1837870.18741.72999999999600741.72999999999635000
-9890.78124218.75.. 114327.97114327.979890.789890.780040000
-15385.8880865.71.. 65479.8365479.8315385.8815385.880045000
;;;;

data do_until;
  obs=_n_;
  set money_table;
  array flow_field [*]  _from_1  _from_2  _from_3   _from_4  _from_5;
  array bal_field [*]   bal_1 bal_2 bal_3  bal_4  bal_5;
  switch_in = 100000;

  do while (switch_in > 0);
    do i=1 to dim(flow_field);
      if bal_field[i] lt 0 and bal_field[i] ne . then
        do;
          flow_field[i] = min(switch_in, abs(bal_field[i]));
          switch_in = switch_in - (abs(bal_field[i]));
/*          output;*/
        end;
        output;
    end;
    n=sum(n,1);
    if n>1000 then leave;
    keep i obs switch_in;
  end;
run;