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Test whether string is a valid integer
...l script. If the user provided a valid integer, the script does one thing, and if not valid, it does something else. Trouble is, I haven't found an easy (and reasonably elegant) way of doing this - I don't want to have to pick it apart char by char.
...
Add UIPickerView & a Button in Action sheet - How?
...ext errors in iOS 7. I just spent a few hours working through this problem and ultimately decided to take a different approach. I replaced the call to show the action sheet with a modal view controller containing a simple tableview.
There are many ways to accomplish this. Here's one way that I jus...
How to change plot background color?
I am making a scatter plot in matplotlib and need to change the background of the actual plot to black. I know how to change the face color of the plot using:
...
MySQL, Check if a column exists in a table with SQL
... query that will check if a specific table in MySQL has a specific column, and if not — create it. Otherwise do nothing. This is really an easy procedure in any enterprise-class database, yet MySQL seems to be an exception.
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How do CSS triangles work?
...ere're plenty of different CSS shapes over at CSS Tricks - Shapes of CSS and I'm particularly puzzled with a triangle:
20...
Why were pandas merges in python faster than data.table merges in R in 2012?
I recently came across the pandas library for python, which according to this benchmark performs very fast in-memory merges. It's even faster than the data.table package in R (my language of choice for analysis).
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How to set Sqlite3 to be case insensitive when string comparing?
...ocase in the column definition (the other options are binary (the default) and rtrim; see here). You can specify collate nocase when you create an index as well. For example:
create table Test
(
Text_Value text collate nocase
);
insert into Test values ('A');
insert into Test values ('b');
i...
In Python, what is the difference between “.append()” and “+= []”?
...d will add one item to the list, while += will copy all elements of right-hand-side list into the left-hand-side list.
Update: perf analysis
Comparing bytecodes we can assume that append version wastes cycles in LOAD_ATTR + CALL_FUNCTION, and += version -- in BUILD_LIST. Apparently BUILD_LIST outw...
Remove duplicated rows using dplyr
...mple(0:1, 10, replace = T),
z = 1:10
)
One approach would be to group, and then only keep the first row:
df %>% group_by(x, y) %>% filter(row_number(z) == 1)
## Source: local data frame [3 x 3]
## Groups: x, y
##
## x y z
## 1 0 1 1
## 2 1 0 2
## 3 1 1 4
(In dplyr 0.2 you won't need...
Difference between toFixed() and toPrecision()?
I'm new to JavaScript and just discovered toFixed() and toPrecision() to round numbers. However, I can't figure out what the difference between the two is.
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