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46 Cards in this Set
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Matrix (N * T) into Vector.

(i1)*T + t

Type of an object?

class(obj)

Eliminate the effect of class.

unclass(obj)

Levels of a factor?

levels(factor)

What is a data.frame?

A list made into a matrix.

Formating in C.

formatC(foo, digits=3)

Formating in C to obtain integers.

formatC(foo, format="d")

Intersection between two vectors.

intersect(vec1,vec2)

Belong to a set.

belong(element,set)
FALSE or TRUE 
Demonstration of plotting maths.

demo(plotmath)

Including mathematical formulaes.

expression()

Combingin maths and variables.

bquote()

Horizontal axis labels.

par(las=1)

Margin intervals.

par(mai=c(1,1,1,1))

Direction of par(mai=c(1,1,1,1))

bottom, left, top, right.

Order and apply an order.

o < order[vec]
order.vec < vec[o] 
Differences between two sets.

setdiff(v1,v2)

Select type of output in SCAN.

scan(foo.txt, what="character)

Add a grid to a graph.

grid(Number_Cells_X, Number_Cells_Y, lwd=2)

Pvalue from ANOVA object.

anova$p

Fvalue from ANOVA object.

anova$F

1:3  2

c(1,0,1)

1:3*2

c(2,4,6)

Close R.

q()

Fit a linear model with DESIGN matrix.

lm.fit(X[n*p], y[n])

Fixed and Random Coefficients in LME.

model$coefficients

Factor to numeric

as.numeric(as.vector(factor))

Is a missing value?

is.na(value)

Max removing missing values.

max(vec, na.rm=TRUE)

Random/Fixed effects from a model.

mod$coefficients

Bash within R.

system("mkdir foo")

Set working directory.

setwd()

Suppress a letter in a string.

strsplit( "foo\", "\")

Write entries in one single column.

write(foo, foo.txt, ncolumns=1)

Matrix Product.

A %*% B

xAx

x %*% A %*% x

Matrix Inverse

solve(A)

xA^{1}x

x %*% solve(A,x)

Permission problem when installing new package.

chown 777 R R

Difference between order() and rank().

x[order(x)] is equivalent to sort(x).
rank(x) is just the ranks. 
gedelete

gedelete

Difference between && and &

&& apply to vectors of length 1.
& apply elementwise to vectors. 
Difference between  and 

 apply to vectors of length 1.
 apply elementwise to vectors. 
Syntax for while.

while (condition) expr

Maximum likelihood estimation.

mle(loglik)

Plot Time series.

plot(as.ts(mat))
