R language Combat-Advanced data Management (1)

1. A data Processing challenge

A. Identification of a single achievement measurement indicator

B. The first 20% students are assessed as a, the next 20% is assessed as B, and so on

C. Sorting students alphabetically

2. Numeric and character processing functions

Numerical functions (mathematics, statistics, probabilities)

Character processing functions

2.1 Mathematical functions

2.2 Statistical functions

> Mean (C (1, 2, 3, 4)) [1] 2.5> > Median (C (1, 2, 3, 4)) [1] 2.5> > SD (C (1, 2, 3, 4)) [1] 1.290994> > var ( C (1, 2, 3, 4)) [1] 1.666667> > Mad (C (1, 2, 3, 4)) [1] 1.4826> > x <-C (1, 2, 3, 4) > y <-quantile (x, C ( .3,.)) > y 30%  84% 1.90 3.52 > > Range (x) [1] 1 4> > diff (Range (x)) [1] 3> > sum (x) [1] 10> ; x <-C (1, 5, max) > diff (x) [1]  4  6> > min (x) [1] 1> > Max (x) [1] 29> > scale (x, center= TRUE, Scale=true)           [, 1][1,] -0.9925397[2,] -0.6984539[3,]  0.6249324[4,]  

2.3 Probability function

> x <-Pretty (C ( -3, 3), +) > x [1] -3.0-2.8-2.6-2.4-2.2-2.0-1.8-1.6-1.4-1.2-1.0-0.8-0.6-0.4-0.2[16]  0.0  0.2  0.4  0.6  0.8  1.0  1.2  1.4  1.6  1.8  2.0  2.2  2.4  2.6  2.8[31]  

2.3.1 Set random number seed

2.3.2 Generating multivariate normal data

> Library (MASS) > Options (digits=3) # Generate random number seeds > set.seed (1234) # specify mean vector, covariance matrix > Mean <-C (230.7, 146.7, 3.6) > Sigma <-Matrix (C (15360.8, 6721.2, -47.1,+                    6721.2, 4700.9, -16.5,+                     -47.1,  -16.5,   0.3), nrow=3, NCOL=3) # generates 500 pseudo-random observation data > MyData <-mvrnorm (x, mean, sigma) # for convenience, results from matrix conversion to Data frame > MyData <-as.data.frame (mydata # Specifies a name for the variable > names (mydata) <-C ("Y", "x1", "X2") # confirms that it has 500 observations and 3 Variables > Dim (MyData) [1]   3# outputs the first 10 observations > head (M Ydata, n=10)       y    x1   x21   98.8  41.3 3.432  244.5 205.2 3.803  375.7 186.7 2.514  -59.2  11.2 4.715  313.0 111.0 3.456  288.8 185.1 2.727  134.8 165.0 4.398  171.7  97.4 3.649  167.2 101.0 3.5010 121.1  

2.4 Character processing function

R language Combat-Advanced data Management (1)