SAS - selecting character observations from position 1 to position 2 - sas

I am stuck in this one particular point. I have a character variable with observations extracted from rtf document. I need to keep only the observations from obs A to obs B. The firstobs and obs is not helpful here because we do not know the observation number beforehand. All we know is the two unique strings. For example in the dataset, I need to create a dataset with observations from obs 11 to 16. This is only part of dataset, the original dataset has over 1500 observations, that is why we use unique text to capture instead of observation number.
Thank you all in advance.

You don't explain enough, but odds are you can do something sort of like this if I understand you right (you have a "start" and a "stop" string in the document).
data want;
set have;
retain keep 0;
if strvar = "keepme" then keep=1;
if keep=1;
if strvar = "lastone" then keep=0;
run;
IE, have some condition set the keep variable to 1, then test for it, then have the off condition after that (assuming you want to keep the off condition row). Use string functions like index or find or scan to search for your particular string if it's not an entire string. You could also use regular expressions if necessary.

Related

Is there any function in SAS where we can read the exact value from the variable

Suppose i have a column called ABC and that variable has the data like
:
123_112233_66778_1122 or
123_112233_1122_11232 or
1122_112233_66778_123
so i want to generate the desire variable in the next column as 1122. like this "1122" i have a long list where i need to cross the value from the column called ABC, if found the exact match then need to generate. However, i don't want to generate the match like 112233 because it does not match the value what i am looking for.
For an example you can see all three line what i have given for reference. I am taking only the match records which is "1122" from all the above 3 lines.
I really have no clue to overcome on the problem. I have tried my hands with wildcards but did not get much success. Any help would be much apricated
It is hard to tell from your description, but from the values you show it looks like you want the INDEXW() function. That will let you search a string for matching words with a option to specify which characters are to be considered as the separators between the words. The result is the location of where the word starts within longer string. When the word is not found the result is a zero.
Let's create a simple example to demonstrate.
data have;
input abc $30. ;
cards;
123_112233_66778_1122
123_112233_1122_11232
1122_112233_66778_123
;
data want;
set have ;
location = indexw(trim(abc),'1122','_');
run;
Note that SAS will consider any value other than zero (or missing) as TRUE so you can just use the INDEXW() function call in a WHERE statement.
data want;
set have;
where indexw(trim(abc),'1122','_');
run;

Iterate data to new rows with line break in SAS

I have multiple lines of data in one field that I need to iterate out to their own rows. The issue is I do not have a traditional delimiter- they are only separated by line breaks. I have tried to use
xp = prxchange('s/[\r+\n]/>/',-1,x) combined with scan, but the prxchange function is not working through the whole block of text. prxchange is only recognizing the first line break and removing the rest of the data. Any idea how to fix or different approaches?
Just use SCAN() to parse the string. No need for the slower speed or complexity of regular expressions.
data want;
set have;
do row=1 to countw(x,'0D0A'x);
line=scan(x,row,'0D0A'x);
output;
end;
run;

SAS Numeric Informat vs Length

I'm trying to determine how SAS is reading the length statement and then the informat statement. I could be misunderstanding, but I'm under the impression that the informat statement for numeric variables worked like this:
informat number 5.;
This would give the variable number the informat 5, allowing 5 numbers to fill it. E.G. 12345
However, when I run the below program, I have a number that has 9 digits, 987654321, with the appropriate length to fit the digits, 6, which will represent all numbers up to 137,438,953,472
Q: is length statement 'overriding' the informat statement and allowing all 9 digits to fill the variable number? How are all 9 digits able to fit in the variable number with an informat of 5.?
data tst;
input number;
length number 6;
informat number 5.;
datalines;
987654321
;
run;
proc print data=tst;
run;
Based on this SAS documentation:
http://support.sas.com/documentation/cdl/en/lrdict/64316/HTML/default/viewer.htm#a000199348.htm
w specifies the width of the input field. Range: 1-32
It would seem that the informat w.d would work as I first described and not allow all 9 digits to fill number
Because you are using list mode input. In that situation SAS reads the next word, however long it is. Essentially in list mode input (including when using the : modifier before an informat specified in the input statement) the width on a informat is ignored.
Other than for creating metadata in the SAS dataset there is not much value in attaching informats like 5. or $10. to variables.
SAS does not need them to understand how to convert text into values, unlike informats like date..
In list mode it ignores the width part.
And in formatted input, where the width matters, you have to specify the informat in the INPUT statement itself.
First off: length is not overriding, or having any impact on, the informat or the read-in. length solely describes how many bytes are used to store the number, nothing more.
For numeric variables, informats don't work quite the intuitive way. I'm not sure why - but they don't.
See this quotation from the list input documentation:
For a character variable, this format modifier reads the value from the next non-blank column until the pointer reaches the next blank column, the defined length of the variable, or the end of the data line, whichever comes first. For a numeric variable, this format modifier reads the value from the next non-blank column until the pointer reaches the next blank column or the end of the data line, whichever comes first.
They do listen to the informat to some extent - add a .2 there and you'll get a forced decimal - but they don't listen to it as to how long of a value to read in. I'm not sure why; it seems intuitive that they should, but they don't.
Here's it with character variables - they respect the length but also ignore the informat:
data tst;
length number $9;
informat number $5.;
input number;
datalines;
987654321
;
run;
proc print data=tst;
run;
Though you do need to put the informat before the input statement (and the length for numeric variables).
More detail is available on the documentation page for INFORMAT:
How SAS Treats Variables When You Assign Informats with the INFORMAT Statement
Informats that are associated with variables by using the INFORMAT statement behave like informats that are used with modified list input. SAS reads the variables by using the scanning feature of list input, but applies the informat.
In modified list input, SAS
does not use the value of w in an informat to specify column positions or input field widths in an external file
uses the value of w in an informat to specify the length of previously undefined character variables
ignores the value of w in numeric informats
uses the value of d in an informat in the same way it usually does for numeric informats
treats blanks that are embedded as input data as delimiters unless you change their status with a DLM= or DLMSTR= option specification in an INFILE statement.
That is much more explicit about the fact that SAS ignores the value of w.
The length of a variable defines the amount of space the value occupies when stored to disk. NOTE: During a running DATA step all numerics are double precision, the truncation to a length < 8 only occurs during output media.
The informat is a separate concept from the length. Informat defines how incoming value representations are to be interpreted for storage as a SAS numeric value. Incoming value representations would be what ever text has to be processed; be it a INPUT statement reading a file, a VIEWTABLE field edit processing a typed in value, an EG grid cell edit, etc...
The format is similarly separate concept that defines how SAS renders a numeric value for output; be it a PUT statement, a VIEWTABLE row render, a placement in a PROCs output, an EG grid cell, etc...
Explanation
Now that that is out of the way, The informat is honored when explicitly stated in an INPUT statement:
data _null_;
attrib number length=6 informat=5.;
input number 5.;
put 'NOTE: ' number=;
datalines;
987654321
run;
===== LOG =====
NOTE: number=98765
And, as you question, the variables associated informat is not applied an explicit numeric informat is not stated
data _null_;
attrib number length=6 informat=5.;
input number;
put 'NOTE: ' number=;
datalines;
987654321
run;
===== LOG =====
NOTE: number=987654321
So the first is LIST input with format specified and the second is a simple LIST input (because no format is specified).
Simple list input will accept some absurdly large data, and the resultant value, while not tail-end precise, will be at the correct exponential level.
data _null_;
attrib number length=6 informat=5.;
input number;
put 'NOTE: ' number= ;
datalines;
123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
run;
===== LOG =====
NOTE: number=1.2345679E89
What do the docs for INPUT Statement, List say ? Certainly nothing about using the variables declared informat when none indicated
Simple List Input
Simple list input places several restrictions on the type of data that
the INPUT statement can read:
• By default, at least one blank must separate the input values. Use
the DLM= or DLMSTR= option or the DSD option in the INFILE statement
to specify a delimiter other than a blank.
• Represent each missing value with a period, not a blank, or two
adjacent delimiters.
• Character input values cannot be longer than 8 bytes unless the
variable is given a longer length in an earlier LENGTH, ATTRIB, or
INFORMAT statement.
• Character values cannot contain embedded blanks unless you change
the delimiter.
• Data must be in standard numeric or character format. (footnote 1)
FOOTNOTE 1: See SAS Language Reference: Concepts for the information about standard and nonstandard data values. (my LOL)
The concepts for "SAS Variable Attributes" states
informat
refers to the instructions that SAS uses when reading data values. If
no informat is specified, the default informat is w.d for a numeric
variable, and $w. for a character variable. You can assign SAS
informats to a variable in the INFORMAT or ATTRIB statement. You can
use the FORMAT procedure to create your own informat for a variable.
(my bold)
Apparently there is no explicit default such as 32. or best32. because values with more than 32 digits will be inputted without error.
So does the documentation explain things ? Yea, well, sorta. What are the take aways:
The human intuition of a numeric variable inheriting its informat during simple list input does not align with the actual implemented behavior.
Tectonic amounts of existing SAS code means a change to implement this intuition is highly unlikely
Simple statements can involve a lot of concepts with wide ranging documentation
Possible change is that the documentation will be updated to be more explicit about the simple list input caveats

SAS - Text Parsing for Case Sensitive Characters

Im having some problems cleaning up free form text strings from a series of notations. The last part of this task involves identifying any names, and removing them from the string. Luckily, all names are U-Cased (always), and the relevant information is placed before the name (always).
My first thought was to use the FIND function to isolate where the name starts, then just output all characters before the starting position...but I could not determine how to use a "wild card" like option to grab the starting position of ANY capital letter. Sample and attempts included below -
DATA SAMPLE;
INPUT TXT $;
CARDS;
firsT
Second
thIrd
foUrth
;
RUN;
Attempt1:
DATA TEST;
SET SAMPLE;
ID = FIND(TXT,'A'-'Z');
RUN;
Attempt2:
DATA TEST;
SET SAMPLE;
ID = FIND(TXT,'A-Z');
RUN;
Clearly both attempts above are not too far from one another, but I could not find (or think) of another approach. Hoping that some mysterious function will come to rescue here...
Assuming I understand what you want to do, you're close - just not doing things the 'SAS' way.
FIND has two siblings, FINDC and FINDW. FINDC finds a single character in a list of characters, which it sounds like what you want to do. It has a lot of options for adding lists of characters; you can't just give it A-Z as that would add those three characters, but you can give it a U option to add uppercase characters.
DATA TEST;
SET SAMPLE;
_endpos= FINDC(TXT,,'u');
ID = substr(TXT,1,_endpos-1);
RUN;

Like operator in SAS datastep

Do we have any alternative for like operator(sql) in SAS datastep?
I am using below code for my requirement. but it is not working.
IF var1 ne : 'ABC' then new_var=XYZ;
Please anyone suggest what is wrong in this or suggest to me what the correct usage is for this situation.
Thanks,
In datastep, 'if' could be used with 'index/find/findw', but if you want to use 'like', you must use 'where' and 'like' together.
data want;
set sashelp.class;
where name like 'A%';
run;
You can use the find function,e.g.:
data want;
set sashelp.class;
if find(name,'e') then new_var='Y';
run;
The colon operator as you've used it only compares values that begin with the quoted string 'ABC'. Essentially SAS compares the 2 values, truncated to the smallest length of the 2. So if all the values in var1 are more than 3 characters, then it will truncate the values to 3 characters before comparing with 'ABC'.
It therefore differs from the like function in sql, which is used in conjunction with the % wildcard operator to determine whether to look at the beginning, end, or anywhere in the string.
To replicate like, you need to use a function such as find as recommended by #Amir, or index which is also commonly used in this situation.