Showing a variable

rivers
##   [1]  735  320  325  392  524  450 1459  135  465  600  330  336  280  315
##  [15]  870  906  202  329  290 1000  600  505 1450  840 1243  890  350  407
##  [29]  286  280  525  720  390  250  327  230  265  850  210  630  260  230
##  [43]  360  730  600  306  390  420  291  710  340  217  281  352  259  250
##  [57]  470  680  570  350  300  560  900  625  332 2348 1171 3710 2315 2533
##  [71]  780  280  410  460  260  255  431  350  760  618  338  981 1306  500
##  [85]  696  605  250  411 1054  735  233  435  490  310  460  383  375 1270
##  [99]  545  445 1885  380  300  380  377  425  276  210  800  420  350  360
## [113]  538 1100 1205  314  237  610  360  540 1038  424  310  300  444  301
## [127]  268  620  215  652  900  525  246  360  529  500  720  270  430  671
## [141] 1770

lenght: How many elements in an array

length(rivers)
## [1] 141

Note that the echo = FALSE parameter was added to the code chunk to prevent printing of the R code that generated the plot.

summary: summary statistics about an array of numbers

summary(rivers)
##    Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
##   135.0   310.0   425.0   591.2   680.0  3710.0

hist: generated a histogram from an array of numbers

# The following command generates a histogram of rivers
hist(rivers, breaks=100)

Dataframe format for datasets

# data.frame function converts a variable to the dataframe format
myrivers <- data.frame(rivers)

#nrow function displays the total number of rows in the dataframe
nrow(myrivers)
## [1] 141
# head funtion displays the first six rows of dataframe
head(myrivers)
##   rivers
## 1    735
## 2    320
## 3    325
## 4    392
## 5    524
## 6    450
# tail function displays the last six rows of dataframe
tail(myrivers)
##     rivers
## 136    500
## 137    720
## 138    270
## 139    430
## 140    671
## 141   1770

Add a new column to a dataframe

myrivers$km <- myrivers$rivers * 1.609

head(myrivers)
##   rivers       km
## 1    735 1182.615
## 2    320  514.880
## 3    325  522.925
## 4    392  630.728
## 5    524  843.116
## 6    450  724.050

```