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Find the day of a week
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df = data.frame(date=c("2012-02-01", "2012-02-01", "2012-02-02"))
df$day <- weekdays(as.Date(df$date))
df
## date day
## 1 2012-02-01 Wednesday
## 2 2012-02-01 Wednesday
## 3 2012-02-02 Thursday
Edit: Just to show another way...
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HashMap get/put complexity
We are used to saying that HashMap get/put operations are O(1). However it depends on the hash implementation. The default object hash is actually the internal address in the JVM heap. Are we sure it is good enough to claim that the get/put are O(1) ?
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Getting the count of unique values in a column in bash
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153
To see a frequency count for column two (for example):
awk -F '\t' '{print $2}' * | sort | un...
What is the JavaScript >>> operator and how do you use it?
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213
It doesn't just convert non-Numbers to Number, it converts them to Numbers that can be expresse...
How can I extract a good quality JPEG image from a video file with ffmpeg?
...le:v (or the alias -q:v) as an output option.
Normal range for JPEG is 2-31 with 31 being the worst quality.
The scale is linear with double the qscale being roughly half the bitrate.
Recommend trying values of 2-5.
You can use a value of 1 but you must add the -qmin 1 output option (because the de...
How do I get the fragment identifier (value after hash #) from a URL?
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No need for jQuery
var type = window.location.hash.substr(1);
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Print a file, skipping the first X lines, in Bash [duplicate]
I have a very long file which I want to print, skipping the first 1,000,000 lines, for example.
13 Answers
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GridLayout and Row/Column Span Woe
...oid:layout_gravity="fill"
android:layout_rowSpan="2"
android:text="1" />
<Button
android:layout_columnSpan="2"
android:layout_gravity="fill_horizontal"
android:text="2" />
<Button
android:layout_gravity="fill_vertical"
android:layout_rowSpan="4"
android:...
Why should eval be avoided in Bash, and what should I use instead?
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152
There's more to this problem than meets the eye. We'll start with the obvious: eval has the p...
How can I get Docker Linux container information from within the container itself?
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14 Answers
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