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Mean per group in a data.frame [duplicate]
..."Rate2"), row.names = c(NA, -9L), class = c("data.table", "data.frame"))
Now to take the mean of Rate1 and Rate2 for all 3 months, for each person (Name):
First, decide which columns you want to take the mean of
colstoavg <- names(mydt)[3:4]
Now we use lapply to take the mean over the column...
Postgres unique constraint vs index
...(ind_id)=(0) already exists.
test=#
It works as expected!
Foreign keys
Now we'll define detail table with two foreign keys referencing to our two columns in master.
create table detail (
con_id integer,
ind_id integer,
constraint detail_fk1 foreign key (con_id) references master(con...
CAP theorem - Availability and Partition Tolerance
...stency. Consider if you have two nodes, X and Y, in a master-master setup. Now, there is a break between network communication between X and Y, so they can't sync updates. At this point you can either:
A) Allow the nodes to get out of sync (giving up consistency), or
B) Consider the cluster to be ...
Data access object (DAO) in Java
...he DAO once we get what we want from the database. Am i right?? and may i know the Scope of this DAO concept rami??
– Vasanth Nag K V
Oct 4 '13 at 6:12
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How to remove remote origin from Git repo
...repo and then added a remote repository using git remote add origin url . Now I want to remove this git remote add origin and add a new repository git remote add origin new-url . How can I do it?
...
Angularjs minify best practice
...t it is also possible to use the first variant safely with ngmin.
UPDATE:
Now ng-annotate becomes a new default tool to solve this issue.
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follo...
Does “git fetch --tags” include “git fetch”?
..., it is not because --tags was set. As such, this special error message is now irrelevant.
To prevent confusion, remove this error message.
With Git 2.11+ (Q4 2016) git fetch is quicker.
See commit 5827a03 (13 Oct 2016) by Jeff King (peff).
(Merged by Junio C Hamano -- gitster -- in commit...
How to create a hash or dictionary object in JavaScript [duplicate]
...
A built-in Map type is now available in JavaScript. It can be used instead of simply using Object. It is supported by current versions of all major browsers.
Maps do not support the [subscript] notation used by Objects. That syntax implicitly cast...
Why doesn't TFS get latest get the latest?
...'t correct. TFS "get latest" works exactly as advertised, as long as TFS knows about changes to the files. Get Latest only "screws up" when people go out and modify filed outside of the IDE without checking them out first. Then, TFS thinks you have the latest source on disk, and doesn't get it.
...
How does a public key verify a signature?
... key to obtain a message, supposedly the same message as (1) but we don't know yet. We now have two messages that we need to verify are identical. So to do this, we will encrypt them both with our public key and compare the two hashes. So we will ....
Encrypt the original message (1) with the public...