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How to succinctly write a formula with many variables from a data frame?
...in a formula to mean all the variables, it is the . identifier.
y <- c(1,4,6)
d <- data.frame(y = y, x1 = c(4,-1,3), x2 = c(3,9,8), x3 = c(4,-4,-2))
mod <- lm(y ~ ., data = d)
You can also do things like this, to use all variables but one (in this case x3 is excluded):
mod <- lm(y ~ ...
Remove the last character in a string in T-SQL?
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SQL MAX of multiple columns?
How do you return 1 value per row of the max of several columns:
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Error: “dictionary update sequence element #0 has length 1; 2 is required” on Django 1.4
I have an error message on django 1.4:
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Underscore: sortBy() based on multiple attributes
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Inserting a PDF file in LaTeX
...myfile.pdf}
To include just the first page of a PDF:
\includepdf[pages={1}]{myfile.pdf}
Run texdoc pdfpages in a shell to see the complete manual for pdfpages.
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Scala @ operator
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180
It enables one to bind a matched pattern to a variable. Consider the following, for instance:
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Finding duplicates in O(n) time and O(1) space
Input: Given an array of n elements which contains elements from 0 to n-1, with any of these numbers appearing any number of times.
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How is a CRC32 checksum calculated?
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118
The polynomial for CRC32 is:
x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 ...
pyplot scatter plot marker size
...d the output they produce.
# doubling the width of markers
x = [0,2,4,6,8,10]
y = [0]*len(x)
s = [20*4**n for n in range(len(x))]
plt.scatter(x,y,s=s)
plt.show()
gives
Notice how the size increases very quickly. If instead we have
# doubling the area of markers
x = [0,2,4,6,8,10]
y = [0]*len(...