I want to define a character array in SAS, I am following this paper. I actually want to have something like
ARRAY test {2} "10,5" "9,0"
so a character array where the characters are numeric. I have not defined them before and the paper they say:
Variables that are not previously defined as character variables will
default to numeric variables unless they are defined as character
variables within the ARRAY stat ement. To define character variables
within the ARRAY statement, place a dollar sign ($) after the
brackets and before any of the variables, as illustrated in this
example
so
ARRAY test {2}$ $"10,5" $"9,0"
but ofcourse this also does not work. What do I have to change?
try using parenthesis. something like below
data have;
ARRAY test {2} $ ("10,5", "9,0");
run;
Related
In a SAS data step, if one creates a character variable he has to be careful in choosing the right length in advance. The following data step returns a wrong result when var1=case2, since 'var2' is truncated to 2 characters and is equal to 'ab', which is obviously not what we want. The same happens replacing var2=' ' with length var2 $2. This kind of procedure is quite prone to errors.
data b; set a;
var2 = ' ';
if var1 = 'case1' then var2='xy';
if var1 = 'case2' then var2='abcdefg';
run;
I was unable to find a way to just define 'var2' as a character, without having to care for its length (side note: if left unspecified, the length is 8).
Do you know if it is possible?
If not, can you perhaps suggest a more robust turnoround, something similar to an sql "case", "decode", etc, to allocate different values to a new string variable that does not suffer from this length issue?
SAS data step code is very flexible compared to most computer languages (and certainly compared to other languages created in the early 1970s) in that you are not forced to define variables before you start using them. The data step compiler waits to define the variable until it needs to. But like any computer program it has rules that it follows. When it cannot tell anything about the variable then it is defined as numeric. If it sees that the variable should be character it bases the decision on the length of the variable on the information available at the first reference. So if the first place you use the variable in your code is assigning it a string constant that is 2 bytes long then the variable has a length of 2. If it is the result of character function where the length is unknown then the default length is 200. If the reference is using a format or informat then the length is set to the appropriate length for the width of the format/informat. If there is no additional information then the length is 8.
You can also use PROC SQL code if you want. In that case the rules of ANSI SQL apply for how variable types are determined.
In your particular example the assignment of blanks to the variable is not needed since all newly created variables are set to missing (all blanks in the case of character variables) when the data step iteration starts. Note that if VAR2 is not new (ie it is already defined in dataset A) then you cannot change its length anyway.
So just replace the assignment statement with a length statement.
data b;
set a;
length var2 $20;
if var1 = 'case1' then var2='ab';
if var1 = 'case2' then var2='abcdefg';
run;
SAS is not going the change the language at this point, they have too many users with existing code bases. Perhaps they will make a new language at some point in the future.
New SAS user.
I'm learning to use/write macros right now. I'm trying to loop through the variable ZONE in a data set "zonelist", as well as count the number of observations in the data set. Here's my code:
data _null_;
set zonelist;
call symput ('zone'||_n_, zone);
call symput ('numzones', _n_);
run;
I expected this to create the variables 'zone1', 'zone2' etc to call them in a do loop. This is a reasonable way to do this, right? Anyway, SAS seems to be adding whitespace to my variable names. I get this error when I run it:
ERROR: Symbolic variable name ZONE 1 must contain only
letters, digits, and underscores. NOTE: Invalid argument to function
SYMPUT('zone '[12 of 16 characters shown],'100 '[12 of
16 characters shown]) at line 567 column 10. zone=100 _ERROR_=1 _N_=1
And of course I get the same error for each observation in my dataset. It makes sense why the ZONE value from the table would have a bunch of whitespace (the variable is $16 I think), but why is it adding all of that space to my variable name? What am I missing here?
This happens due to the numeric / character conversion of the _n_ variable. When numeric values are converted to character, they are right aligned.
Try the following instead:
data _null_;
set zonelist;
call symputx(cats('zone',_n_), zone);
call symputx('numzones', _n_);
run;
The cats function will perform the numeric / character conversion and also strip the leading blanks.
If you have SAS 9 then you can also use the symputX function to strip leading / trailing blanks from the macro VALUES as well.
I solved it using "compress", to just delete all of the spaces:
data _null_;
set zonelist;
call symputx(compress('zone',_n_), zone);
call symputx('numzones', _n_);
run;
However, this doesn't help me understand why I needed to do this at all. Any enlightenment would be appreciated!
SAS has two types of variables, fixed length character strings and floating point numbers. Let's look at your first statement.
call symput ('zone'||_n_, zone);
In there you are referencing two variables and one string literal. Since the || operator works on character variables SAS will need to do an implicit conversion of the numeric variable _n_ to a character string. SAS will use the best12. format so it will result in a value like ' 1'. So you will end up with an invalid value for the call symput() function to use for the macro variable name.
But what about that third value, the variable zone? If zone is a number then the same implicit conversion will happen and the macro variable will end up containing leading spaces. Or the zone variable is a character string, in which case your macro variable will most likely end up having trailing spaces, unless the length of the value of zone happens to exactly match the maximum length that the variable zone is defined to hold.
As others have suggested there are two things to do to fix this.
First use the call symputx() instead of call symput() (unless you really want those trailing spaces stored in your macro variables) which will automatically strip() the input values. It will also silence the note about implicit numeric to character conversion.
The second is to use some method of generating the macro varaible name that does not insert spaces. The easiest way is to just use the cats() function instead of the || operator. But you could also use combinations of other functions like put(), compress(), strip(), etc.
call symputx(cats('zone',_n_),zone);
Is there a way to access a character in a string in fortran? If I wanted to store the first letter of a the string "taco" in a character variable how would I do that?
Character variables and constants can be "substringed" using a syntax similar to an array section.
a_character_variable = "taco"(1:1)
A substring of a character variable is also a variable - it may appear on the left hand side of an assignment statement.
I imagine what I'm asking is pretty basic, but I'm not entirely certain how to do it in SAS.
Let's say that I have a range of variables, or an array, x1-xn. I want to be able to run a program that uses the number of variables within that range as part of its calculation. But I want to write it in such a way that, if I add variables to that range, it will still function.
Essentially, I want to be able to create a variable that if I have x1-x6, the variable value is '6', but if I have x1-x7, the value is '7'.
I know that :
var1=n(of x1-x6)
will return the number of non-missing numeric variables.. but I want this to work if there are missing values.
I hope I explained that clearly and that it makes sense.
Couple of things.
First off, when you put a range like you did:
x1-x7
That will always evaluate to seven items, whether or not those variables exist. That simply evaluates to
x1 x2 x3 x4 x5 x6 x7
So it's not very interesting to ask how many items are in that, unless you're generating that through a macro (and if you are, you probably can have that macro indicate how many items are in it).
But the range x1--x7 or x: both are more interesting problems, so we'll continue.
The easiest way to do this is, if the variables are all of a single type (but an unknown type), is to create an array, and then use the dim function.
data _null_;
x3='ABC';
array _temp x1-x7;
count = dim(_temp);
put count=;
run;
That doesn't work, though, if there are multiple types (numeric and character) at hand. If there are, then you need to do something more complex.
The next easiest solution is to combine nmiss and n. This works if they're all numeric, or if you're tolerant of the log messages this will create.
data _null_;
x3='ABC';
count = nmiss(of x1-x7) + n(of x1-x7);
put count=;
run;
nmiss is number of missing, plus n is number of nonmissing numeric. Here x3 is counted with the nmiss group.
Unfortunately, there is not a c version of n, or we'd have an easier time with this (combining c and cmiss). You could potentially do this in a macro function, but that would get a bit messy.
Fortunately, there is a third option that is tolerant of character variables: combining countw with catx. Then:
data _null_;
x3='ABC';
x4=' ';
count = countw(catq('dm','|',of x1-x7),'|','q');
put count=;
run;
This will count all variables, numeric or character, with no conversion notes.
What you're doing here is concatenating all of the variables together with a delimiter between, so [x1]|[x2]|[x3]..., and then counting the number of "words" in that string defining word as thing delimited by "|". Even missing values will create something - so .|.|ABC|.|.|.|. will have 7 "words".
The 'm' argument to CATQ tells it to even include missing values (spaces) in the concatenation. The 'q' argument to COUNTW tells it to ignore delimiters inside quotes (which CATQ adds by default).
If you use a version before CATQ is available (sometime in 9.2 it was added I believe), then you can use CATX, but you lose the modifiers, meaning you have more trouble with empty strings and embedded delimiters.
According to the manual, string concatenation isn't implemented in gdb. I need it however, so is there a way to achieve this, perhaps using array functions?
I don't have a copy of gdb around to try this on, but perhaps this line from later in the Ada section of the document will help you?
Rather than use catenation and
symbolic character names to introduce
special characters into strings, one
may instead use a special bracket
notation, which is also used to print
strings. A sequence of characters of
the form ["XX"]' within a string or
character literal denotes the (single)
character whose numeric encoding is XX
in hexadecimal. The sequence of
characters["""]' also denotes a
single quotation mark in strings. For
example, "One line.["0a"]Next
line.["0a"]"
contains an ASCII newline character
(Ada.Characters.Latin_1.LF) after each
period.
For Objective-C:
[#"asd" stringByAppendingString:#"zxc"]
[#"ID: " stringByAppendingString:(NSString*) [aTaskDict valueForKey:#"ID"]]