grouping elements from a table
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eric capnu
am 7 Sep. 2017
Kommentiert: eric capnu
am 19 Sep. 2017
Hi everyone:
i have a table like this:
Week Open High Low Close
---- ---- ---- --- -----
10 1.2 1.4 1.1 1.2
10 1.5 1.7 1.5 1.6
10 1.4 2.1 1.3 2
10 2.2 2.4 2 2.1
11 2 2.1 2 2
11 2.2 2.5 1.1 1.3
12 1.7 1.9 1.6 1.6
12 1.8 1.9 0.6 1.4
12 0.9 1.4 0.8 1
is there a way to get the first element(open), maximum element(high), minimum element(low) and last element (close) for each week? so the result table would be
Week Open High Low Close
---- ---- ---- --- -----
10 1.2 2.4 1.1 2.1
11 2 2.5 1.1 1.3
12 1.7 1.9 0.6 1
thanks in advance
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Akira Agata
am 8 Sep. 2017
Assuming your table is T, the following code can generate what you want.
[group, id] = findgroups(T.Week);
func = @(p, q, r, s) [p(1), max(q), min(r), s(end)];
result = splitapply(func, T.Open, T.High, T.Low, T.Close, group)
Tout = array2table([id, result],...
'VariableNames', T.Properties.VariableNames);
3 Kommentare
Walter Roberson
am 18 Sep. 2017
>> findgroups([1 2.5 2 2.5 1])
ans =
1 3 2 3 1
Looks like it works for double to me.
Weitere Antworten (1)
Guillaume
am 8 Sep. 2017
Step 1: define a function in its own m file that applies the appropriate filter to each column (unfortunately, you can't use anonymous functions for this):
function [firstopen, maxhigh, minlow, lastclose] = filtercols(open, high, low, close)
firstopen = open(1); %first element
maxhigh = max(high);
minlow = min(low);
lastclose = close(end); %last element
end
t = array2table([
10 1.2 1.4 1.1 1.2
10 1.5 1.7 1.5 1.6
10 1.4 2.1 1.3 2
10 2.2 2.4 2 2.1
11 2 2.1 2 2
11 2.2 2.5 1.1 1.3
12 1.7 1.9 1.6 1.6
12 1.8 1.9 0.6 1.4
12 0.9 1.4 0.8 1], ...
'VariableNames', {'Week', 'Open', 'High', 'Low', 'Close'});
result = rowfun(@filtercols, t, 'GroupingVariable', 'Week', 'NumOutputs', 4, 'OutputVariableNames', {'Open', 'High', 'Low', 'Close'})
The only potential issue is that the order in which the rows are grouped together by rowfun is not documented, so it may be that the first element and last element are not the correct ones. In my version of matlab (R2017a), it is correct.
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