Question

The following bit of SAS code is supposed to read from a dataset which contains a numeric variable called Radvalue . Radvalue is the temperature of a radiator, and if a radiator is switched off but then its temperature increases by 2 or more it s a sign that it has come on, and if it is on but its temperature decreases by 2 or more it s a sign that it s gone off. Radstate is a new variable in the dataset which indicates for every observation whether the radiator is on or off, and it s this I m trying to fill in automatically for the whole dataset. So I m trying to use the LAG function, trying to initialise the first row, which doesn t have a dif_radvalue, and then trying to apply the algorithm I just described to row 2 onwards. Any idea why the columns Radstate and l_radstate come out completely blank?

Thanks everso much!! Let me know if I haven t explained the problem clearly.

Data work.heating_algorithm_b;
 Input ID Radvalue; 
 Datalines; 
  1 15.38 
  2 15.38 
  3 20.79 
  4 33.47 
  5 37.03 
  6 40.45 
  7 40.45 
  8 40.96 
  9 39.44 
  10 31.41 
  11 26.49 
  12 23.06 
  13 21.75 
  14 20.16 
  15 19.23 
 ; 

DATA temp.heating_algorithm_c;
 SET temp.heating_algorithm_b;

 DIF_Radvalue = Radvalue - lag(Radvalue);

 l_Radstate = lag(Radstate);

 if missing(dif_radvalue) then  
  do;
   dif_radvalue = 0;
   radstate = "off"; 
  end;                            
 else if l_Radstate = "off"  &  DIF_Radvalue > 2    then Radstate = "on";
 else if l_Radstate = "on" &  DIF_Radvalue < -2  then  Radstate = "off";
 else  Radstate = l_Radstate;
run;

Answer 1

你们正试图在产出数据组(RADSTATE)现有的变量上履行LAG职能。我用一个RETAIN取代了关于RAASTATE的LAG。另外,你也有权不附带任何条件逻辑。采用以下代码。

Data work.heating_algorithm_b;
 Input ID Radvalue; 
 Datalines; 
  1 15.38 
  2 15.38 
  3 20.79 
  4 33.47 
  5 37.03 
  6 40.45 
  7 40.45 
  8 40.96 
  9 39.44 
  10 31.41 
  11 26.49 
  12 23.06 
  13 21.75 
  14 20.16 
  15 19.23 
 ; 

DATA work.heating_algorithm_c;
 length radstate $3;
 retain radstate;
 SET work.heating_algorithm_b;

 old_radvalue=lag(radvalue);

 if _n_=1 then do;
  dif_radvalue=0;
  radstate="off";
 end;
 else do;
  DIF_Radvalue = Radvalue-Old_Radvalue;

  if Radstate = "off"  &  DIF_Radvalue > 2    then Radstate = "on";
  else if Radstate = "on" &  DIF_Radvalue < -2  then  Radstate = "off";
  /* Else Radstate stays the same */
 end;
run;

Answer 2

我没有待命安排制度的经验,但也许需要一份<条码>(l_Radstate)的核对,以便第一次通过,例如:

if missing(l_Radstate) then
do; radstate = "off"; end;

我认为,只有在以下情况下才需要这样做:Rad Value - lag(Rad Value)没有强迫DIF_Rad Value。如果是的话,我不相信会帮助......。

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