[R] / Operator not meaningful for factors

[Vivek Satsangi]

Folks,
I have a very basic question. The solution eludes me perhaps because
of my own lack of creativity. I am not attaching a fully reproducible
session because the issue may well be becuase of the way the data file
is, and the data file is large (and I don't know whether I can legally
distribute it). If people can suggest things that might be wrong in my
data or the way that I am reading it, I would be most grateful.

I get the following error message in the session quoted at the end of
this email:
/ not meaningful for factors in: Ops.factor(BookValuePS, Price)

As you can see in that some session, I check that the two vectors
being divided are numeric. I also check that the divisor is not 0 at
any index. I also believe that this is not because of the NA's in the
data. My question is, what are other "problems" that can cause the /
operator to not be meaningful?

I did try some simple examples to try to get the same error. However, 
I am not sure how to put the same NA's that one  gets from
read.table() into a vector:
> a <- c(1, 2, 3, NA);
> a
[1]  1  2  3 NA
> b <- c( 1, 2, 3, 4);
> c <- b / a;
> b
[1] 1 2 3 4
> a <- c(1, 2, 3, );
> c <- b/a;
Warning message:
longer object length
        is not a multiple of shorter object length in: b/a


******** Quoted Session below ********
 > explainPriceSimplified <- read.table("combinedClean.csv",
+                            sep = ",", header=TRUE);
> attach(explainPriceSimplified);
> summary(explainPriceSimplified);
     Symbol           Date              Price            EPS          
   BookValuePS
 XL     :   98   Min.   :19870630   22     :   61   Min.   :-1.401e+05
  Min.   :-6.901e+05
 ZION   :   97   1st Qu.:19910930   26.5   :   61   1st Qu.: 4.650e-01
  1st Qu.: 3.892e+00
 YRCW   :   72   Median :19960331   27.5   :   58   Median : 1.060e+00
  Median : 7.882e+00
 AA     :   71   Mean   :19957688   30     :   58   Mean   :-1.534e+01
  Mean   : 1.515e+02
 ABS    :   71   3rd Qu.:20001231   25     :   56   3rd Qu.: 1.890e+00
  3rd Qu.: 1.444e+01
 ABT    :   71   Max.   :20041231   (Other):29561   Max.   : 5.309e+03
  Max.   : 3.366e+06
 (Other):29624                      NA's   :  249   NA's   : 2.460e+02
  NA's   : 4.760e+02
 FiscalQuarterRep    F12MRet
 2004/2F:  482    Min.   :-100.00
 2003/4F:  471    1st Qu.:  -8.82
 2004/1F:  470    Median :  10.57
 2004/3F:  470    Mean   :  13.36
 2003/3F:  464    3rd Qu.:  31.12
 2003/2F:  463    Max.   :4700.00
 (Other):27284    NA's   : 463.00
> mode(Price)
[1] "numeric"
> mode(EPS)
[1] "numeric"
> mode(BookValuePS)
[1] "numeric"
> BP <- BookValuePS / Price ;
Warning message:
/ not meaningful for factors in: Ops.factor(BookValuePS, Price)
> which(Price==0)
numeric(0)
>


--
-- Vivek Satsangi
Student, Rochester, NY USA