I want to a drop a great number of string variables that contain the word "Other" in their observations. As such, I tried the following loop to drop all the variables:
foreach var of varlist v1-v240 {
drop `var' if `var'=="Other"
}
What I get in return is the answer "syntax error". I would like to know not only a way to perform the task of dropping all the variables that contain the word "Other", but also why the code that I've entered returns an error.
The short answer on why your syntax is illegal, which #Dimitriy Masterov doesn't quite spell out, is that drop supports just two syntaxes, which can't be mixed, dropping variables and dropping observations. This is documented: see e.g. http://www.stata.com/help.cgi?drop and the corresponding on-line help and manual entry within Stata.
In addition to other solutions, findname from the Stata Journal would allow this solution:
findname, any(# == "Other")
drop `r(varlist)'
Your interpretation of contain is evidently 'is equal to' judging by your use of == as an operator, echoed above. If contain really means 'includes as substring', then you need a syntax such as
any(strpos(#, "Other"))
or
any(regexm(#, "Other"))
as #Dimitriy also explains.
If they are actual strings, this should work:
sysuse auto, clear
ds, has(type string) // get a list of string variables
// loop over each string variable, count observations that contain Buick anywhere, and drop the variable if N>0
foreach var of varlist `r(varlist)' {
count if regexm(`var',"Buick")
if r(N)>0 {
drop `var'
}
}
If "contains" means only contains, then you need to use "^Buick$" instead or
count if `var'=="Buick"
Beware of leading/trailing spaces.
The if qualifier restricts the scope of a command to those observations for which the value of the expression is true. Your code errors because you are asking Stata to drop a variable (a column) if some observations (rows) satisfy a condition. You could use the if qualifier to drop those observations or you can drop a variable, but not both simultaneously. My code uses the if command (a different beast) to verify the condition, and then drops the variable if that condition is satisfied.
You might be tempted to do something like
if `var'=="Other" {
drop `var'
}
but that will usually not work as expected (it would drop the variable only if the first observation was "Other").
Related
I've been trying use matchAll in node.js, but when I run the code and log the return value it only shows Object [RegExp String Iterator] {}.
Could you help me to understand why this is the case?
Be mindful of the types of things you are working with.
To quote the docs for String.prototype.matchAll:
The matchAll() method returns an iterator of all results matching a string against a regular expression, including capturing groups.
(Emphasis mine.)
So, you get an iterator. What is an iterator? Well, the docs say:
In JavaScript an iterator is an object which defines a sequence and potentially a return value upon its termination.
[...]
While it is easy to imagine that all iterators could be expressed as arrays, this is not true. Arrays must be allocated in their entirety, but iterators are consumed only as necessary. Because of this, iterators can express sequences of unlimited size, such as the range of integers between 0 and Infinity.
So, matchAll will only do the actual work of finding the next match when you ask for it, by asking for next value of the iterator, and the amount of state that has to be kept won't increase that much with a longer string because not all matches have to be remembered at once. That's the beauty of iterators (and their opposite part, generators).
This is also why you won't see all the results in your console when printing the iterator - otherwise, a matchAll on a very very large string would cause a long delay and high CPU usage when its return value is merely logged to the console, which wouldn't make sense.
You can use the result of matchAll in a for of loop, which will look for the next match every time the loop repeats:
for (const match of 'abcde'.matchAll(/./g)) {
console.log(match)
}
// Prints 5 times something like ['a', index: 0, input: 'abcde', groups: undefined ]
Or, if you are willing to forgo the benefit of on-demand matching, you can extract all values from the iterator at once and fit them into an array using either spread syntax or Array.from:
const allMatches = [...'abcde'.matchAll(/./g)]
// - or -
const allMatches = Array.from('abcde'.matchAll(/./g))
(In fact, the spread syntax is shown in the example at the very top of the matchAll docs too.)
I get two integer's passed into a puppet class and I want to loop over resources based on the range of integers between the two. I can't quite figure out the syntax to do so. The best I have is similar to the following:
e.g.
$start_int=4
$end_int=15
$end_int.each |$number| { if $number >= $start_int {...} }
Is there a better way to loop over a given integer range?
You can create an actual array and iterate that. Sadly, the stdlib range function will not yet accept actual numbers (at the time of writing this) so you will need to convert to String.
range("$start_int", "$end_int").each |$number| { ... }
Today Puppet accepts integers as arguments for range, so the accepted answer could be rephrased to:
range($start_int, $end_int).each |$number| { ... }
(so the quotes around $start_int and $end_ind are no longer necessary)
So I was getting a notice in my php while creating a google product feed.
The notice was
"The following php notice has occurred 4989 times on the _ site today:
PHP Notice: Undefined index: 0 in /xxx/Status.php on line 583"
This was the code in that class
public function inStockLocally($productcode)
{
if($this->_status[$productcode]['status'] == self::IN_STOCK) {
return $this->_status[$productcode]['in_stock_local'];
}
return false;
}
The function was getting a $productcode = 0, but the productcode was infact 'w32', so the key didn't exist.
up the stack where the function was being called I put this in, in order to break on the troublesome product.
if ($productcode == 0) {
$test = 'breakhere';
}
Using netbeans and firebug, it broke on the line when $productcode = 'w32'
So my question is why does 'w32' == 0 evaluate to true?
It is also evaluating to true with other similar structure codes like 'h94'.
Any help would be appreciated as no one in the department can figure out why this is happening.
I guess I didn't put enough info in the q. Two things going on.
1. 'w32' converted to a number = 0 for some reason. 2. [0] is being inserted as my key in the array when the productcode has the structure 'x##';
I'm a little new here, so pardon if this isn't the answer you were expecting, but PHP does a lot of automatic type conversion. So any string that doesn't start with a numeric character (0..9, +, -, etc) will evaluate to zero.
"If you compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically. "
http://php.net/manual/en/language.operators.comparison.php
Additionally, I suppose you have an indexed array, although you expect it to be an associative array:
The array() function is used to create an array.
In PHP, there are three types of arrays:
Indexed arrays - Arrays with numeric index
Associative arrays - Arrays with named keys
Multidimensional arrays - Arrays containing one or more arrays
Syntax
Syntax for indexed arrays:
array(value1,value2,value3,etc.);
Syntax for associative arrays:
array(key=>value,key=>value,key=>value,etc.);
I've got a variable that could be a number of types - sometimes it's a string, sometimes a number, table or bool. I'm trying to print out the value of the variable each time like this:
print("v: "..v)
with v being my variable. Problem is, when I get a value that can't be concatenated I get this error:
myscript.lua:79: attempt to concatenate a table value
I've tried changing it to this in case it manages to detect whether or not the variable can be printed:
print("v: "..(v or "<can't be printed>"))
but I had the same problem there. Is there some sort of function I can use to determine if a variable can be concatenated to a string, or a better way of printing out variables?
You can provide the values as separate arguments to print:
print("v:", v)
This would print something like
v: table: 006CE900
Not necessarily the most useful, but better than a crash if it's just for debugging purposes.
See here for information on more useful table printing.
tostring(v) works for all possible v values (including nil). So writing your line as:
print( "v: " .. tostring( v ) )
will always work.
Alternatively you could have a look at type( v ) and if its "string" print it, otherwise print something else (if that's what you want).
There are some other questions on here that are similar but sufficiently different that I need to pose this as a fresh question:
I have created an empty class, lets call it Test. It doesn't have any properties or methods. I then iterate through a map of key/value pairs, dynamically creating properties named for the key and containing the value... like so:
def langMap = [:]
langMap.put("Zero",0)
langMap.put("One",1)
langMap.put("Two",2)
langMap.put("Three",3)
langMap.put("Four",4)
langMap.put("Five",5)
langMap.put("Six",6)
langMap.put("Seven",7)
langMap.put("Eight",8)
langMap.put("Nine",9)
langMap.each { key,val ->
Test.metaClass."${key}" = val
}
Now I can access these from a new method created like this:
Test.metaClass.twoPlusThree = { return Two + Three }
println test.twoPlusThree()
What I would like to do though, is dynamically load a set of instructions from a String, like "Two + Three", create a method on the fly to evaluate the result, and then iteratively repeat this process for however many strings containing expressions that I happen to have.
Questions:
a) First off, is there simply a better and more elegant way to do this (Based on the info I have given) ?
b) Assuming this path is viable, what is the syntax to dynamically construct this closure from a string, where the string references variable names valid only within a method on this class?
Thanks!
I think the correct answer depends on what you're actually trying to do. Can the input string be a more complicated expression, like '(Two + Six) / Four'?
If you want to allow more complex expressions, you may want to directly evaluate the string as a Groovy expression. Inside the GroovyConsole or a Groovy script, you can directly call evaluate, which will evaluate an expression in the context of that script:
def numNames = 'Zero One Two Three Four Five Six Seven Eight Nine'.split()
// Add each numer name as a property to the script.
numNames.eachWithIndex { name, i ->
this[name] = i
}
println evaluate('(Two + Six) / Four') // -> 2
If you are not in one of those script-friendly worlds, you can use the GroovyShell class:
def numNames = 'Zero One Two Three Four Five Six Seven Eight Nine'.split()
def langMap = [:]
numNames.eachWithIndex { name, i -> langMap[name] = i }
def shell = new GroovyShell(langMap as Binding)
println shell.evaluate('(Two + Six) / Four') // -> 2
But, be aware that using eval is very risky. If the input string is user-generated, i would not recommend you going this way; the user could input something like "rm -rf /".execute(), and, depending on the privileges of the script, erase everything from wherever that script is executed. You may first validate that the input string is "safe" (maybe checking it only contains known operators, whitespaces, parentheses and number names) but i don't know if that's safe enough.
Another alternative is defining your own mini-language for those expressions and then parsing them using something like ANTLR. But, again, this really depends on what you're trying to accomplish.