Postgres documentation seems to only show how to check if two arrays have overlapping elements.
I need to know if the two array have non-overlapping elements.
So if I have 2 arrays:
array_1 = '{1, 2, 3, 4}'
array_2 = '{0, 3, 4, 5}'
This should return false. Checking for not equal doesn't work because they may not be equal in that one array might have the same integer repeat several times.
Is this comparison possible?
Two sets are non-overlapping if there are no elements in common, so using the && operator for arrays and negating the result give you what you want.
# select NOT (ARRAY[1,2,3,4] && ARRAY[0,3,3,3,3,4,5]) AS non_overlapping;
non_overlapping
-----------------
f
(1 row)
# select NOT (ARRAY[1,2,8,9] && ARRAY[0,3,3,3,3,4,5]) AS non_overlapping;
non_overlapping
-----------------
t
(1 row)
Related
I am using cp_model to solve a problem very similar to the multiple-knapsack problem (https://developers.google.com/optimization/bin/multiple_knapsack). Just like in the example code, I use some boolean variables to encode membership:
# Variables
# x[i, j] = 1 if item i is packed in bin j.
x = {}
for i in data['items']:
for j in data['bins']:
x[(i, j)] = solver.IntVar(0, 1, 'x_%i_%i' % (i, j))
What is specific to my problem is that there are a large number of fungible items. There may be 5 items of type 1 and 10 items of type 2. Any item is exchangeable with items of the same type. Using the boolean variables to encode the problem implicitly assumes that the order of the assignment for the same type of items matter. But in fact, the order does not matter and only takes up unnecessary computation time.
I am wondering if there is any way to design the model so that it accurately expresses that we are allocating from fungible pools of items to save computation.
Instead of creating 5 Boolean variables for 5 items of type 'i' in bin 'b', just create an integer variable 'count' from 0 to 5 of items 'i' in bin 'b'. Then sum over b (count[i][b]) == #item b
Say we have a kdb list
L1:(1 2 3 4 5)
Apply condition
L1 < 3
And how can I retrieve result in another list (1 2)
You can use the where keyword for this:
q)l1 where l1<3
1 2
Applying l1<3 will return a list of booleans 11000b. Using where on this list will return the index of every 1b
q)where 11000b
0 1
Then indexing back into the original list will return the result in another list.
I have a 29736 x 6 table, which is referred to as table_fault_test_data. It has 6 columns, with names wind_direction, wind_speed, air_temperature, air_pressure, density_hubheight and Fault_Condition respectively. What I want to do is to label the data in the Fault_Condition (last table column with either a 1 or a 0 value, depending on the values in the other columns.
I would like to do the following checks (For eg.)
If wind_direction value(column_1) is below 0.0040 and above 359.9940, label 6 th column entry corresponding to the respective row of the table as a 1, else label as 0.
Do this for the entire table. Similarly, do this check for others
like air_temperature, air_pressure and so on. I know that if-else
will be used for these checks. But, I am really confused as to how I
can do this for the whole table and add the corresponding value to
the 6 th column (Maybe using a loop or something).
Any help in this
regard would be highly appreciated. Many Thanks!
EDIT:
Further clarification: I have a 29736 x 6 table named table_fault_test_data . I want to add values to the 6 th column of table based on conditions as below:-
for i = 1:29736 % Iterating over the whole table row by row
if(1st column value <x | 1st column value > y)
% Add 0 to the Corresponding element of 6 th column i.e. table_fault_test_data(i,6)
elseif (2nd column value <x | 2nd column value > y)
% Add 0 to the Corresponding element of 6 th column i.e. table_fault_test_data(i,6)
elseif ... do this for other cases as well
else
% Add 1 to the Corresponding element of 6 th column i.e. table_fault_test_data(i,6)
This is the essence of my requirements. I hope this helps in understanding the question better.
You can use logical indexing, which is supported also for tables (for loops should be avoided, if possible). For example, suppose you want to implement the first condition, and also suppose your x and y are known; also, let us assume your table is called t
logicalIndecesFirstCondition = t{:,1} < x | t{:,2} >y
and then you could refer to the rows which verify this condition using logical indexing (please refer to logical indexing
E.g.:
t{logicalIndecesFirstCondition , 6} = t{logicalIndecesFirstCondition , 6} + 1.0;
This would add 1.0 to the 6th column, for the rows for which the logical condition is true
I have an integer array of length 2000 elements. For ex
x = [2, 4, 5, 6, 5,6,7,5......];
Now in this array i need to find an element which occurs repeatedly. For ex I need to know how many times a number '5' has been occurred. In the above example it is three times.
Is there any way to search an matching element and returns the count in matlab?
Do you know the number in advance?
If so, to work out how many times it appears in x you could do:
sum(x==5)
The x==5 creates a vector of [FALSE FALSE TRUE FALSE TRUE FALSE FALSE TRUE ...], being TRUE whenever x is 5.
The sum then adds up that vector, where FALSE maps to 0 and TRUE to 1.
A quick way get the count is
sum(x == 5)
If you need the indicies of the matching elements:
find(x == 5)
Notice, the count is also length(find(x == 5)).
Standard caveats apply toward the use of == and floating point numbers.
I am looking for to take one particular number or range of numbers from a set of number?
Example
A = [-10,-2,-3,-8, 0 ,1, 2, 3, 4 ,5,7, 8, 9, 10, -100];
How can I just take number 5 from the set of above number and
How can I take a range of number for example from -3 to 4 from A.
Please help.
Thanks
I don't know what you are trying to accomplish by this. But you could check each entry of the set and test it it's in the specified range of numbers. The test for a single number could be accomplished by testing each number explicitly or as a special case of range check where the lower and the upper bound are the same number.
looping and testing, no matter what the programming language is, although most programming languages have builtin methods for accomplishing this type of task (so you may want to specify what language are you supposed to use for your homework):
procfun get_element:
index=0
for element in set:
if element is 5 then return (element,index)
increment index
your "5" is in element and at set[index]
getting a range:
procfun getrange:
subset = []
index = 0
for element in set:
if element is -3:
push element in subset
while index < length(set)-1:
push set[index] in subset
if set[index] is 4:
return subset
increment index
#if we met "-3" but we didn't met "4" then there's no such range
return None
#keep searching for a "-3"
increment index
return None
if ran against A, subset would be [-3,-8, 0 ,1, 2, 3, 4]; this is a "first matched, first grabbed" poorman's algorithm. on sorted sets the algorithms can get smarter and faster.