Is there a specific way I can limit the number of true predicates available using a specified fact?
At the moment I have total(2). as a fact.
I thought this would work:
:- total(N), #count{x:something_to_limit(x)} = K, K=N.
However this doesn't limit the number of something_to_limit predicates to the specified total(2) fact where N would equal 2.
Any help would be greatly appreciated:)
The x in x:something_to_limit(x) is a constant symbol, you probably want to use variables X. The constraint
:- total(N), #count{X:something_to_limit(X)} = K, K=N.
should work.
Related
I want to create a variable called 'flag_artifact' where certain subjects from my dataset (for whom I know have bad quality images) are coded as e.g., 1. My dataset is stored in a table T with a certain number of rows and 'subject' is the 1st column in the table.
I managed to do it by creating a for loop. Surely there is a more efficient way to do this by perhaps directly creating the variable and using less lines of code? Could anyone give some advice?
Thank you very much! Here is what I have:
flag_artifact = {'T_300'}; %flagging subject number 300 for example
for i = 1:size(T,1)
if isequal(table2cell(T(i, 1)), flag_artifact)
T(i, 1) = {'1'};
end
end
However, when creating the variable flag_artifact = {'T_300'}, I would like it to include more than one subject. I tried using flag_artifact = {'T_300'}; {'T_301'}, as well as flag_artifact = {'T_300', 'T_301'} but it doesn't work because these subject identifiers do not get replaced with 1s.
In my code, I have a structure and in a field of it, I want to sort its values.
For instance, in the field of File_Neg.name there are the following values, and They should be sorted as the right values.
File_Neg.name --> Sorted File_Neg.name
'-10.000000.dcm' '-10.000000.dcm'
'-102.500000.dcm' '-12.500000.dcm'
'-100.000000.dcm' '-100.000000.dcm'
'-107.500000.dcm' '-102.500000.dcm'
'-112.500000.dcm' '-107.500000.dcm'
'-110.000000.dcm '-110.000000.dcm'
'-12.500000.dcm' '-112.500000.dcm'
There is a folder that there are some pictures with negative labels in it (above example are labels of pictures). I want to get them in the same order as present in the folder(that's mean the Sorted File_Neg.name). But when running the following code the values of Files_Neg.name load as the above example (left: File_Neg.name), while I want the right form.
I have also seen this and that but they didn't help me.
How to sort values of a field in a structure in Matlab?
Files_Neg = dir('D:\Rename-RealN');
File_Neg = dir(strcat('D:\Rename-RealN\', Files_Neg.name, '\', '*.dcm'));
% when running the code the values of Files_Neg.name load as the above example (left: File_Neg.name)
File_Neg.name:
This answer to one of the questions linked in the OP is nearly correct for the problem in the OP. There are two issues:
The first issue is that the answer assumes a scalar value is contained in the field to be sorted, whereas in the OP the values are char arrays (i.e. old-fashioned strings).
This issue can be fixed by adding 'UniformOutput',false to the arrayfun call:
File_Neg = struct('name',{'-10.000000.dcm','-102.500000.dcm','-100.000000.dcm','-107.500000.dcm','-112.500000.dcm','-110.000000.dcm','-12.500000.dcm'},...
'folder',{'a','b','c','d','e1','e2','e3'});
[~,I] = sort(arrayfun(#(x)x.name,File_Neg,'UniformOutput',false));
File_Neg = File_Neg(I);
File_Neg is now sorted according to dictionary sort (using ASCII letter ordering, meaning that uppercase letters come first, and 110 still comes before 12).
The second issue is that OP wants to sort according to the magnitude of the number in the file name, not using dictionary sort. This can be fixed by extracting the value in the anonymous function applied using arrayfun. We use str2double on the file name, minus the last 4 characters '.dcm':
[~,I] = sort(arrayfun(#(x)abs(str2double(x.name(1:end-4))),File_Neg));
File_Neg = File_Neg(I);
Funnily enough, we don't want to use 'UniformOutput',false any more, since the anonymous function now returns a scalar value.
Postgresql 10+
Example from the documentation...
jsonb_set('[{"f1":1,"f2":null},2,null,3]', '{0,f1}','[2,3,4]', false)
results in...
[{"f1":[2,3,4],"f2":null},2,null,3]
Fair enough. But I need to find my target node by attribute value, not index. For the life of me, I cannot figure out how do something like...
jsonb_set('[{"f1":1,"f2":null},2,null,3]', '{(where f1 = 1),f1}','[2,3,4]', false)
Any advice on how to accomplish this?
Thanks!
You can split the steps into two jobs:
Split in elements (jsonb_arral_elements)
Indentify wich elements must change (case when...)
Update that element (jsonb_set)
Join all together (jsonb_agg)
solution
select jsonb_agg(case when element->>'f1'='1' then jsonb_set(element, '{f1}', '[2,3,4]') else element end)
from jsonb_array_elements('[{"f1":1,"f2":null},2,null,3,{"f1":3},{"f1":1,"f2":2}]'::jsonb) element
note
I changed the input adding two more elements with "f1" key
Is there a neat way of looking up the key of a dictionary by an atom value if that atom is inside a value list ?
Assumption: The value lists of the dictionary have each unique elements
Example:
d:`tech`fin!(`aapl`msft;`gs`jpm) / would like to get key `fin by looking up `jpm
d?`gs`jpm / returns `fin as expected
d?`jpm / this doesn't work unfortunately
$[`jpm in d`fin;`fin;`tech] / this is the only way I can come up with
The last option does not scale well with the number of keys
Thanks!
You can take advantage of how where operates with dictionaries, and use in :
where `jpm in/:d
,`fin
Note this will return a list, so you might need to do first on the output if you want to replicate what you have above.
Why are you making this difficult on yourself? Use a table!
q)t:([] c:`tech`tech`fin`fin; sym:`aapl`msfw`gs`jpm)
q)first exec c from t where sym=`jpm
You can of course do what you're asking:
first where `jpm in'd
but this doesn't extend well to vectors while the table-approach does!
q)exec c from t where sym in `jpm`gs
I think you can take advantage of the value & key keywords to find what you're after:
q)key[d]where any value[d]in `jpm
,`fin
Hope that helps!
Jemma
The answers you have received so far are excellent. Here's my contribution building on Ryan's answer:
{[val;dict]raze {where y in/:x}[dict]'[val]}[`msft`jpm`gs;d]
The main difference is that you can pass a list of values to be evaluated and the result will be a list of keys.
[`msft`jpm`gs;d]
Output:
`tech`fin`fin
I'd like to make a loop in Matlab that would work only over user specified intervals of time, instead of simply the whole time. How can one write this loop condition?
regards
Generally you and iterate multiple ways. There are two main ways that I can think of off the top of my head. I will also open this up for community wiki so others can just easily edit this as well.
First, using a simple For loop.
The general syntax is for index = 1:someValue
someValue can really be anything that is greater than 1 in this case. Many times it's simply the last index value of a matrix you're wanting to traverse.
You can modify this as well though! Let's say you want every 3rd index starting with the 2nd position in the matrix. All you have to do is: for index = 2:3:someValue The 3 here tells the loop that it should add 3 to the index at the end of each loop iteration until you get to (or surpass) someValue.
Yet another modfication is traversing backwards. In this case you start at the 'end' and move to the beginning. It would look like this: for index = someValue:-1:1 You can also do every 4th index while going backwards for index = someValue:-4:1.
Obviously you can replace the value between the two : to be a step size that you want. You just have to be aware of potential indexing issues that can arrise. Namely trying to index out of bounds of the matrix or potentially going negative.
Secondly here you can modify the value within the loop itself. Generally this isn't the best idea when you're using a for loop as the value of your indexing variable will be changed by the loop as well as by you within the loop. Many times you'll see this done with a while loop or a do while combo.
A few examples are as follows:
index = 0;
do
{
% some operations
index = index + aNumber;
}while(index <= someValue)
In the above example the loop will continue to loop until the index value index becomes greater than or equal to someValue at the end of the current iteration of the loop. This type of loop will ALWAYS, and I repeat ALWAYS execute at least once.
index = 0;
while(index <= someValue)
{
%some operations
index = index + aNumber;
}
In this case the loop will continue to loop while index satisfies the logical statement here. If the statement isn't true when you try to run the loop for the first time it will not execute at all.
Hope this helps and feel free to ask for any additional clarification if you want it!
Others, please feel free to edit to add additional information or clean up what I might have not explained fully =)
Do you mean something like this:
for i = [1:5 7:10 12:14 21:22]
do_func(i)
end
or even
for i = [1:5 4:7 19:-1:15]
do_func(i)
end
?
If you only want to perform an action when a certain condition is true in a loop, you just need something like:
for i=1:length(arr)
if condition(arr(i))
do_something(arr(i));
end
end