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Cluster analysis in R: determine the optimal number of clusters
...rst, some reproducible data (the data in the Q are... unclear to me):
n = 100
g = 6
set.seed(g)
d <- data.frame(x = unlist(lapply(1:g, function(i) rnorm(n/g, runif(1)*i^2))),
y = unlist(lapply(1:g, function(i) rnorm(n/g, runif(1)*i^2))))
plot(d)
One. Look for a bend or elbo...
How do I get the day of week given a date?
...
# leap year correction
dayOfWeek += aux / 4 - aux / 100 + (aux + 100) / 400
# sum monthly and day offsets
dayOfWeek += offset[month - 1] + (day - 1)
dayOfWeek %= 7
return dayOfWeek, week[dayOfWeek]
print weekDay(2013, 6, 15) == (6, 'Saturda...
View array in Visual Studio debugger? [duplicate]
...ee a subsection of the array you can type this into the watch window;
ptr+100,10
to show a list of the 10 elements starting at ptr[100]. Beware that the displayed array subscripts will start at [0], so you will have to remember that ptr[0] is really ptr[100] and ptr[1] is ptr[101] etc.
...
Truncate (not round) decimal places in SQL Server
...
Here's the way I was able to truncate and not round:
select 100.0019-(100.0019%.001)
returns 100.0010
And your example:
select 123.456-(123.456%.001)
returns 123.450
Now if you want to get rid of the ending zero, simply cast it:
select cast((123.456-(123.456%.001)) as decima...
Can dplyr package be used for conditional mutating?
...x) sample(7, 1e7, TRUE)))
setnames(DT, letters[1:6])
# > dim(DT)
# [1] 10000000 6
DF <- as.data.frame(DT)
DT_fun <- function(DT) {
DT[(a %in% c(0,1,3,4) | c == 4), g := 3L]
DT[a %in% c(2,5,7) | (a==1 & b==4), g := 2L]
}
DPLYR_fun <- function(DF) {
mutate(DF, g =...
What is the difference between svg's x and dx attribute?
...eight', 500);
svg.append("line").attr('x1', 0).attr('x2', 500).attr('y1', 100).attr('y2', 100);
svg.append("line").attr('x1', 0).attr('x2', 500).attr('y1', 200).attr('y2', 200);
group = svg.selectAll("g")
.data(dataset)
.enter()
.append("g");
// Without the dy=0.35em offset
group.appe...
How can I be notified when an element is added to the page?
... solution than the one presented here. Seriously. Don't poll the DOM every 100 milliseconds; it will waste CPU power and your users will hate you.
Since mutation events were deprecated in 2012, and you have no control over the inserted elements because they are added by someone else's code, your on...
CSS endless rotation animation
...ting 2s linear infinite;
}
<div
class="rotating"
style="width: 100px; height: 100px; line-height: 100px; text-align: center;"
>Rotate</div>
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...
Fixed point vs Floating point number
... For example, I might want to keep two digits of precision, so a value of 100 means actually means 1.00, 101 means 1.01, 12345 means 123.45, etc.
Floating point numbers are more general purpose because they can represent very small or very large numbers in the same way, but there is a small penalt...
JavaScript variables declare outside or inside loop?
...ou've got yourself an accidental global.
In particular:
for (var i; i<100; i++)
do something;
for (var i; i<100; i++)
do something else;
Crockford will recommend you remove the second var (or remove both vars and do var i; above), and jslint will whinge at you for this. But IMO it...