data management and statistical analysis - loading data
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8/8/2019 Data Management and Statistical Analysis - Loading data
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LOADING DATALOADING DATALOADING DATALOADING DATA
Data Managementand Statistical analysis
Import file to R – read.table()
• read.table() reads a file in a table format
and creates a dataframe from it.
• Usage
> read.table(file, header=FALSE,
sep=“”, …)
# file – name of the file
# header – a logical value indicating
whether the file contains the names of
the variables as its first line
# sep – field separator character
1. Change the default working directory
• Right-click on your R shortcut→Select Properties
• Opposite the “Start in”, change the
starting directory from where yourfiles are saved (eg. R-OBJECT/ My
RData)
• Click Apply
Changing the Default Directory
2. Change the default working directory (More temporarily)
• From the main window of R, select File→ Change dir
• Change the starting directory from where your files are saved
(eg. R-OBJECT/ My RData)
• Click Ok.
Changing the Default Directory
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Loading a .xls File : odbcConnectExcel()
• Open connections to ODBC data in excel file
• The following scripts reads data from excel file using
RODBC package
> # Reads the data from an excel table or query
> library(RODBC);
> cname<-odbcConnectExcel(“filename.xls");
> qname <- "SELECT * FROM Sheet_name$;"
> dframe_name <- sqlQuery(cname, qname);
> odbcClose(cname);
# odbcClose() close connection to ODBC database
Loading a .CSV Text File : read.table()
> # Reads the data from .csv text file
> dframe_name <- read.table(“filename.CSV",
> sep = ",",
> header = TRUE);
• read.table() reads a data file in a table format and
creates a dataframe from it.
• The following scripts reads data from a .csv text file usingthe read.table utility
Loading a .mdb database File :odbcConnect Access()
• Open connections to ODBC databases
• The following scripts reads data from Access database
using RODBC package
> # Reads the data from an access table or query
> cname<-odbcConnectAccess(“filename.mdb");
> qname <- "SELECT * FROM Sheet_name$;"
> dframe_name <- sqlQuery(cname, qname);
> odbcClose(cname);
> # Checks if the data is available in R
> is.data.frame(dframe_name);
• View objects available in workspace
> ls()
Some useful commands
[1] "a" "a1" "connect" "ids" "Irrig" "newtra"
[7] "query" "RF_early" "RF_late" "srdta" "srdta1" "x"
• Remove an object
> rm()
> rm(newtra)
• Remove all objects
> rm(list=ls())
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Some useful commands : str()
• Displays the structure of an R object
> str(datasetname)
> str(RF_late)
'data.frame': 24 obs. of 8 variables:
$ LINE : int 1 1 1 2 2 2 3 3 3 4 ...
$ REP : int 1 2 3 1 2 3 1 2 3 1 ...
$ RLD0 : num 2.71 6.09 12.12 7.07 4.6 ...
$ RLD15: num 0.329 0.434 1.084 0.462 0.496 ...
$ RMD0 : num 0.193 0.298 1.391 0.313 0.153 ...
$ RMD15: num 0.008 0.019 0.04 0.014 0.02 0.008
0.008 0.007 0.012 0.014 ...
$ TTLRW: num 30.2 47.5 216.7 49 25.9 ...
$ BMSS : num NA NA NA 15.7 10.8 ...
Some useful commands
• List contents of an object
> datasetname
> RF_late
LINE REP RLD0 RLD15 RMD0 RMD15 TTLRW BMSS
1 1 1 2.710 0.329 0.193 0.008 30.18 NA
2 1 2 6.086 0.434 0.298 0.019 47.49 NA
3 1 3 12.116 1.084 1.391 0.040 216.71 NA
. . .
24 8 3 14.324 0.763 0.860 0.023 132.42 72.68
• To save all the results of calculations done, the
functions created, and the packages loaded in the
memory
Click File/Save Workspace
• To load workspace
Click File/Load Workspace
Saving and restoring workspace
THANK YOU!Please do Exercise A ☺☺☺☺
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