I was asked to find the length of First defined in the program below and I think it should be 15 but the answer says it is 200.
My thought is that SCAN(Author,1,',') has value Agatha, but since I did not define its length the length is as same as Author, which is 15. Again, First is valued as A since its the first letter of Agatha, but because of not specifying the length is still 15.
data test;
Author='Agatha Christie';
First=substr(scan(Author,1,','),1,1);
run;
proc contents;
run;
I have no clue where 200 comes from... can I get some help?
Before SAS 9.4, the variable length returned from Scan function used to be 200.
But SAS 9.4 variable length give in the scan function is same as the variable it operates on. hence new variable length will be 15 not 200 as said by #Craig. below is information for SAS 9.4 documentation.
In a DATA step, if the SCAN function returns a value to a variable that has not yet been given a length, that variable is given the length of the first argument. This behavior is different from the behavior in previous releases of SAS. In previous releases, code that created a variable with a length of 200 might have produced a variable with a length that was greater than expected. If you need the SCAN function to assign a variable with a value that is different from the length of the first argument, use a LENGTH statement.
The answer is wrong. It's 15.
x
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);
I am getting the following errors/warnings:
WARNING: Apparent symbolic reference ARRAY_MONTH_COUNT not resolved.
ERROR: Too many variables defined for the dimension(s) specified for the array array1.
ERROR 22-322: Syntax error, expecting one of the following: an integer constant, *.
ERROR 200-322: The symbol is not recognized and will be ignored.
for the following code:
data demo_effective;
set work.demo;
array array1 [&array_month_count] $ 1 membsdemo_flag_&start_yrmo
membsdemo_flag_&end_yrmo;
length yrmo 6;
do i=1 to &array_month_count;
if array1[i] = 'N' then continue;
if array1[i] = 'Y' then yrmo = substrn(vname(array1[i]),20,6);
output;
end;
run;
I didn't write this program, I am just trying to work with it, so I don't know why this isn't working (I made no changes, just ran the program in SAS and it was already broken), and I am still learning SAS and SQL, so half of this program is nonsense to me even after watching some videos and trying to find more information about it.
If it helps, it looks like the warning/errors are occurring around array1 [&array_month_count].
&array_month_count is a macro variable. In SAS, this is a string that is substituted at compile time. Macros "write" code.
It looks like all the errors you are getting are because that variable does not have a value.
So somewhere in the code, there should be something that sets the value of array_month_count. Find that, fix it, and this step should work.
A bit more detail than Dom's answer may be helpful, though his answer is certainly the crux of the issue.
&array_month_count needs to be defined, but you also probably have a few other issues.
array array1 [&array_month_count] $ 1 membsdemo_flag_&start_yrmo
membsdemo_flag_&end_yrmo;
This is probably wrong, or else this code is perhaps doing something different from what it used to: I suspect it is intended to be
array array1 [&array_month_count] $ 1 membsdemo_flag_&start_yrmo - membsdemo_flag_&end_yrmo;
In other words, it's probably supposed to expand to something like this.
array array1 [6] $ 1 membsdemo_flag_1701 membsdemo_flag_1702 membsdemo_flag_1703 membsdemo_flag_1704 membsdemo_flag_1705 membsdemo_flag_1706;
The 6 there isn't actually needed since the variables are listed out (in a condensed form). The dash tells SAS to expand numerically with consecutive numbers from the start to the end; it would only work if your yrmo never crosses a year boundary. It's possible -- is appropriate instead - it tells SAS to expand in variable number order, which works fine if you have consecutively appearing variables (in other words, they're adjacent when you open the dataset).
The 6 is however needed for the second bit.
do i=1 to &array_month_count;
Unless you rewrite it to this:
do i = 1 to dim(array1); *dim = dimension, or count of variables in that array;
In which case you really don't even need that value.
--
If it's actually intended to be the code as above, and only have 2 variables, then you don't need &array_month_count since it's known to be only 2 variables.
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.
Apologies for such an entirely uninformed question, but I don't know any SAS and just need to know what one line of code does, so I hope someone can help.
I have a loop over an array of variables, and an if clause that is based on a comparison to .Z, but this variable is defined nowhere, so I'm guessing this is some sort of SAS syntax trick. Here's the loop:
ARRAY PTYPE{*} X4216 X4316 X4416 X4816 X4916 X5016;
DO I=1 TO DIM(PTYPE);
IF (PTYPE{I}<=.Z) THEN PUT &ID= PTYPE{I}=;
END;
So on the first iteration, the loop would check whether the value in X4216 is smaller than .Z, and then...? ID is another varuable in the dataset, but I have no idea what's happening on the right hand side of that if clause. I've briefly consulted the SAS documentation to figure out that ampersands refer to macros, but my knowledge of SAS is to limited to understand what's happening.
Can anyone enlighten me?
.Z is a special missing value. In SAS a missing value (what you might call a NULL value) is indicated by a period. There are also 27 other special missing values that are indicated by a period followed by a letter or an underscore. The missing values are distinct and are all considered smaller than any actual number. .Z is the "largest". So PTYPE{I}<=.Z is basically testing if the value is missing. You could instead use MISSING(PTYPE{I}) to make the same test. The right hand side is writing out the name and the value of the variable in the array with a missing value and also the name and value of the variable named in the macro variable ID.