I am a new user in GAMS and I want to write a condition but I cannot figure out the right way to express it.
I want b(l) to be equals Pcost(pl) when Loc(l,pl) is not zero.
Is there any way to express this?
b(l) = sum(pl$Loc(l,pl), Pcost(pl));
The $ is the condition sign. pl needs to be controlled on the right. Therefore, the sum is used. Assuming, that there is just one pl for each l with Loc(l,pl)>0, the assignment above will do, what you asked for.
Note: $Loc(l,pl) can be read as "if Loc(l,pl) is unequal to zero. If you want to be more explicit, you could also write the following (which is really the same as the first version for GAMS):
b(l) = sum(pl$(Loc(l,pl)<>0), Pcost(pl));
Related
I've looked through a number of tutorials and asks, and haven't found a working solution to my problem.
Suppose my dataset has two columns: sort_order and field_value. sort_order is an integer and field_value is a numerical (10,2).
I want to format some rows as #,#0 and others as #,#0.00.
Normally I would just do
iif( fields!sort_order.value = 1 or fields!sort_order.value = 23 or .....
unfortunately, the list is fairly long.
I'd like to do the equivalent of if fields!sort_order.value in (1,2,21,63,78,...) then...)
As recommended in another post, I tried the following (if sort in list, then just output a 0, else a 1. this is just to test the functionality of the IN operator):
=iif( fields!sort_order.Value IN split("1,2,3,4,5,6,8,10,11,15,16,17,18,19,20,21,26,30,31,33,34,36,37,38,41,42,44,45,46,49,50,52,53,54,57,58,59,62,63,64,67,68,70,71,75,76,77,80,81,82,92,98,99,113,115,116,120,122,123,127,130,134,136,137,143,144,146,147,148,149,154,155,156,157,162,163,164,165,170,171,172,173,183,184,185,186,192,193,194,195,201,202,203,204,210,211,212,213,263",","),0,1)
However, it doesn't look like the SSRS expression editor wants to accept the "IN" operator. Which is strange, because all the examples I've found that solve this problem use the IN operator.
Any advice?
Try using IndexOf function:
=IIF(Array.IndexOf(split("1,2,3,4,...",","),fields!sort_order.Value)>-1,0,1)
Note all values must be inside quotations.
Consider the recommendation of #Jakub, I recommend this solution if
your are feeding your report via SP and you can't touch it.
Let me know if this helps.
I tried to match the sql values string (0),(5),(12),... or (0,11),(122,33),(4,51),... or (0,121,12),(31,4,5),(26,227,38),... and so on with the regular expression
\(\s*\d+\s*(\s*,\s*\d+\s*)*\)(\s*,\s*\(\s*\d+\s*(\s*,\s*\d+\s*)*\))*
and it works. But...
How can I ensure that the regex does not match a values string like (0,12),(1,2,3),(56,7) with different number of columns?
Thanks in advance...
As i mentioned in comment to the question, the best way to check if input string is valid: contains the same count of numbers between brackets, is to use client side programm, but not clear SQL.
Implementation:
List<string> s = new List<string>(){
"(0),(5),(12)", "(0,11),(122,33),(4,51)",
"(0,121,12),(31,4,5),(26,227,38)","(0,12),(1,2,3),(56,7)"};
var qry = s.Select(a=>new
{
orig = a,
newst = a.Split(new string[]{"),(", "(", ")"},
StringSplitOptions.RemoveEmptyEntries)
})
.Select(a=>new
{
orig = a.orig,
isValid = (a.newst
.Sum(b=>b.Split(new char[]{','},
StringSplitOptions.RemoveEmptyEntries).Count()) %
a.newst.Count()) ==0
});
Result:
orig isValid
(0),(5),(12) True
(0,11),(122,33),(4,51) True
(0,121,12),(31,4,5),(26,227,38) True
(0,12),(1,2,3),(56,7) False
Note: The second Select statement gets the modulo of sum of comma instances and the count of items in string array returned by Split function. If the result isn't equal to zero, it means that input string is invalid.
I strongly believe there's a simplest way to achieve that, but - at this moment - i don't know how ;)
:(
Unless you add some more constraints, I don't think you can solve this problem only with regular expressions.
It isn't able to solve all of your string problems, just as it cannot be used to check that the opening and closing of brackets (like "((())()(()(())))") is invalid. That's a more complicated issue.
That's what I learnt in class :P If someone knows a way then that'd be sweet!
I'm sorry, I spent a bit of time looking into how we could turn this string into an array and do more work to it with SQL but built in functionality is lacking and the solution would end up being very hacky.
I'd recommend trying to handle this situation differently as large scale string computation isn't the best way to go if your database is to gradually fill up.
A combination of client and serverside validation can be used to help prevent bad data (like the ones with more numbers) from getting into the database.
If you need to keep those numbers then you could rework your schema to include some metadata which you can use in your queries, like how many numbers there are and whether it all matches nicely. This information can be computed inexpensively from your server and provided to the database.
Good luck!
I am reading someone else sql and his code was like this
There is view called user_v with column path as Array
select * from user_v where 'USER_TYPE'=path[2]
can't i use
path[2] = 'USER_TYPE'
This is a precaution taken by some programmers in languages where assignment and comparison can be easily confused, such as C or PHP, where the following statement looks innocent:
if ( $foo = 1 )
but it is actually assigning 1 to $foo, and the if will always evaluate to true (in PHP, at least, where 1 is true). What was meant was if ( $foo == 1 ).
If you reverse the arguments, the error becomes obvious sooner:
if ( 1 = $foo ) # SYNTAX ERROR
if ( 1 == $foo ) # Desired behaviour
This is sometimes known as "yoda coding", and is in the coding standards of Wordpress, for example.
See also: Why put the constant before the variable in a comparison?
In SQL, there is less chance of such a muddle, since although = can mean either assignment or comparison, there are rarely situations where a typo would select the wrong meaning.
However, if the coding standards for every other language used by a project mandate it, it would make sense to reinforce the habit by also using it in SQL, since I can't think of a specific reason not to write it that way.
There is no difference at all.
It's psychology.
You would want to read someone else's code out laud and say:
Where my column equals 2.
When you read:
Where 2 equals my column
you have to stop for a while, return, explain it to yourself.
We maintain all of these rules that seem rubish at first glance just to make other people lives easier.
I'm trying to figure out if there's a way in mathematica where I can solve for particular variables when given other variables and a set of equations. Essentially there are 6 variables, and I'm given 3 of them and have to calculate the others using these equations-
Variables-
B,Qs,f0,R,c,L
Equations-
f0=1/(2*Pi*Sqrt[L*c])
Qs=(w*L)/R
w=2*Pi*f0
B=f0/Qs
We are given the values of any 3 of those variables and have to figure out the rest using those values.
I was thinking perhaps using Eliminate but I'm not sure exactly how that would be structured as I've only used it previously with set variables that don't change and a single output.
When using the Solve function with Mathematica, you can specify for what variables you want Solve to specify the solutions. Note that Solve may not be able to find expressions in terms of these variables (if the equations you give it are contradictory or insufficient) or for all values as some functions have no inverse or only partial inverses.
Your question looks a lot like homework in Electromagnetics, but here is an example with your original problem. You will have to adapt these ideas to give to Solve the set of variables you are looking for. Also remember to use == to specify equality testing. A simple = is for immediate assignment to a variable.
Solve[{f0 == 1/(2*Pi*Sqrt[L*c]), Qs == (w*L)/R, w == 2*Pi*f0, B == f0/Qs}, {f0, B, c}]
{{f0->w/(2 [Pi]), B->w/(2 [Pi] Qs), c->L/(Qs^2 R^2)}}
Was wondering if someone could lend me their expertise. Pretty new to Vb.net and have come across this conditional statement in one of our products. Could someone please confirm the validity of the statement and explain what's going on here? I've tried numerous searches, but I cannot find anything related.
If (IsDBNull(dr("someID")), "0", dr("someID")) = someID.ToString() Then
I have changed the "id" value names as it's code from a commercial product, but the ID's used were all the same variable (ints).
Thanks for any input you can offer on this!
Joe
PS: The reason I can't check this at run time is because of how the product operates.
It is an inline If statement
If(condition,iftrue,iffalse) if condition is true evaluate and return iftrue else iffalse
The If operator in VB.NET 2008 acts as a ternary operator.[ REFERENCE]
Example:
Dim foo as String = If(bar = buz, cat, dog) 'Condition satisfied then it'll return cat else dog.
The statement is checking to see if the dr("SomeID") equals the value someID.ToString. The reason the If is required is because you need to check if the dr("someID") Is Null. If it is 0 is used instead which presumably should not be equal to someID.
It is the same as doing the following:
If Not IsDBNull(dr("someID")) Then
If dr("someID").ToString = someID.ToString Then
End If
End If
I would suggest that something like this would be more appropriate (checking integer values instead of comparing strings)
If(IsDBNull(dr("someID")), 0, CInt(dr("someID"))) = someID Then
I would also suggest Turning Option Strict On as the code you posted should not compile!