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question regarding totals
Samuel Chen
Samuel Chen
Posted
12 years ago
Hi there,
I'd like to find out the total amount when the dates are the same. What is the best method when the data set has 3000 - 4000 rows?
{{{1, 1, 2000}, 2}, {{1, 2, 2000}, 1}, {{1, 2, 2000}, .2}}
Please help. Thanks.
SamĀ
POSTED BY:
Samuel Chen
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Nick Gaskill
Nick Gaskill
Posted
12 years ago
There's also a useful how-to in Documentation that talks about this...
How to Perform Operations on Subgroups of Data
POSTED BY:
Nick Gaskill
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Vitaliy Kaurov
Vitaliy Kaurov, WOLFRAM Research
Posted
12 years ago
You can also use
GatherBy[...]
:
{#[[1, 1]], Total[#[[All, 2]]]} & /@ GatherBy[data, #[[1]] &]
Apply
Sort[...]
to the final result if your dates will come out unsorted.
POSTED BY:
Vitaliy Kaurov
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Arnoud Buzing
Arnoud Buzing, Wolfram Research
Posted
12 years ago
That's better, yes.
Or even:
GatherBy[ data, First ]
POSTED BY:
Arnoud Buzing
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Arnoud Buzing
Arnoud Buzing, Wolfram Research
Posted
12 years ago
Does this work for you?
Map[
{#[[1, 1]], Total[#[[All, 2]]]} &,
Gather[list, SameQ[First[#], First[#2]] &]
]
POSTED BY:
Arnoud Buzing
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