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How to write a simple database engine [closed]
...h pattern of delimiter is never used in your data itself. i.e. if you have selected <*> for example to separate columns, you should validate the data you are placing in this table not to contain this pattern. you could also use a row header and a column header by specifying size of row and som...
MySQL how to join tables on two fields
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SELECT *
FROM t1
JOIN t2 USING (id, date)
perhaps you'll need to use INNEER JOIN or
where t2.id is not null
if you want results only matching both conditions
...
pull out p-values and r-squared from a linear regression
... need. The beta, se, t and p vectors are stored in it. Get the p-values by selecting the 4th column of the coefficients matrix (stored in the summary object):
summary(fit)$coefficients[,4]
summary(fit)$r.squared
Try str(summary(fit)) to see all the info that this object contains.
Edit: I had ...
jQuery hasAttr checking to see if there is an attribute on an element [duplicate]
...
What about api.jquery.com/has-attribute-selector
– Aamir Afridi
Jan 30 '13 at 14:19
3
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pandas: filter rows of DataFrame with operator chaining
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Since version 0.18.1 the .loc method accepts a callable for selection. Together with lambda functions you can create very flexible chainable filters:
import numpy as np
import pandas as pd
df = pd.DataFrame(np.random.randint(0,100,size=(100, 4)), columns=list('ABCD'))
df.loc[lambda ...
Convert data.frame columns from factors to characters
... can create a logical vector of which columns are factors, and use that to selectively apply factor
f <- sapply(bobf, class) == "factor"
bobc[,f] <- lapply(bobc[,f], factor)
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ERROR 1452: Cannot add or update a child row: a foreign key constraint fails
... table. Following query would be helpful to fetch those non-matching rows:
SELECT child_table.*
FROM child_table
LEFT JOIN parent_table
ON parent_table.referenced_column = child_table.referencing_column
WHERE parent_table.referenced_column IS NULL
Now, you can generally do one (or more) of th...
What are some methods to debug Javascript inside of a UIWebView?
...e sure "Show Develop Menu in Menubar" is on.
From the Menu-bar (of Safari) select Develop -> iPhone Simulator -> [your webview page].
That's it !
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Start a git commit message with a hashmark (#)
...y that behavior is wanted.
git 2.0.x/2.1 (Q3 2014) will add an automatic selection for core.commentChar:
See commit 84c9dc2
When core.commentChar is "auto", the comment char starts with '#' as in default but if it's already in the prepared message, find another char in a small subset. This should...
Rails: How to change the title of a page?
...In rails 3 content_for is smart enough to work correctly with caching (see selected answer).
– opsb
Nov 15 '11 at 10:41
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