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How to drop columns by name in a data frame
... function. For example :
R> df <- data.frame(x=1:5, y=2:6, z=3:7, u=4:8)
R> df
x y z u
1 1 2 3 4
2 2 3 4 5
3 3 4 5 6
4 4 5 6 7
5 5 6 7 8
Then you can use the which function and the - operator in column indexation :
R> df[ , -which(names(df) %in% c("z","u"))]
x y
1 1 2
2 2 3
3 3 4...
How to find the length of a string in R
...
424
See ?nchar. For example:
> nchar("foo")
[1] 3
> set.seed(10)
> strn <- paste(samp...
How to count the number of true elements in a NumPy bool array
...erDavid Alber
15.1k66 gold badges5757 silver badges6464 bronze badges
2
...
What's the difference between lists enclosed by square brackets and parentheses in Python?
... = {}
>>> z[x] = 3
>>> z
{(1, 2): 3}
>>> z[y] = 4
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
Note that, as many people have pointed out, you can add tuples together. For example:
>>>...
efficient circular buffer?
...range(20):
... d.append(i)
...
>>> d
deque([10, 11, 12, 13, 14, 15, 16, 17, 18, 19], maxlen=10)
There is a recipe in the docs for deque that is similar to what you want. My assertion that it's the most efficient rests entirely on the fact that it's implemented in C by an incredibly s...
No provider for “framework:jasmine”! (Resolving: framework:jasmine)
...n": "0.0.0",
"dependencies": {},
"devDependencies": {
"grunt": "~0.4.1",
"grunt-autoprefixer": "~0.4.0",
"grunt-bower-install": "~0.7.0",
"grunt-concurrent": "~0.4.1",
"grunt-contrib-clean": "~0.5.0",
"grunt-contrib-coffee": "~0.7.0",
"grunt-contrib-compass": "~0.6.0"...
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How do I check out version version/tag 1.1.4 of the rspec bundle ?
2 Answers
2
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Creating Multifield Indexes in Mongoose / MongoDB
...
4 Answers
4
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Numpy index slice without losing dimension information
...Joe Kington
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6
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Pandas dataframe get first row of each group
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248
>>> df.groupby('id').first()
value
id
1 first
2 first
3 first
4 ...