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What are the special dollar sign shell variables?
...ipeline exit status.
$! is the PID of the most recent background command.
$0 is the name of the shell or shell script.
Most of the above can be found under Special Parameters in the Bash Reference Manual. There are all the environment variables set by the shell.
For a comprehensive index, please ...
How to create circle with Bézier curves?
...
10 Answers
10
Active
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How to avoid scientific notation for large numbers in JavaScript?
...tific notation if the number is >= 1e21 and has a maximum precision of 20. Other than that, you can roll your own, but it will be messy.
function toFixed(x) {
if (Math.abs(x) < 1.0) {
var e = parseInt(x.toString().split('e-')[1]);
if (e) {
x *= Math.pow(10,e-1);
x = ...
Use find command but exclude files in two directories
... it happy.
– peelman
Nov 12 '13 at 20:08
3
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How to access cookies in AngularJS?
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200
This answer has been updated to reflect latest stable angularjs version. One important note is ...
Two statements next to curly brace in an equation
...cument}
\begin{equation}
f(x)=\begin{cases}
1, & \text{if $x<0$}.\\
0, & \text{otherwise}.
\end{cases}
\end{equation}
\end{document}
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...
add a string prefix to each value in a string column using Pandas
...['col'].astype(str)
Example:
>>> df = pd.DataFrame({'col':['a',0]})
>>> df
col
0 a
1 0
>>> df['col'] = 'str' + df['col'].astype(str)
>>> df
col
0 stra
1 str0
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Understanding how recursive functions work
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107
I think the confusion is stemming from thinking of it as "the same function" being called many ...
pandas read_csv and filter columns with usecols
...andas as pd
from StringIO import StringIO
csv = r"""dummy,date,loc,x
bar,20090101,a,1
bar,20090102,a,3
bar,20090103,a,5
bar,20090101,b,1
bar,20090102,b,3
bar,20090103,b,5"""
df = pd.read_csv(StringIO(csv),
header=0,
index_col=["date", "loc"],
usecols=["date", "loc", "x"],
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Return 0 if field is null in MySQL
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Use IFNULL:
IFNULL(expr1, 0)
From the documentation:
If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.
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