R – How to calculate mean vector of data set in R

meanobjectrvector

I'm very new to R, so please bear with me.

Given test data in a .txt file…

Num   height   weight   class  
1     72.1     147.5    1  
2     75.2     125.4    1
3     60.3     102.3    2
4     62.4     98.2     2
5     50.5     74.1     3

I read the file into R by:

testdata <- read.table("testdata.txt", header = TRUE)

which creates the data with 15 obs. of 4 variables. I can assign each column to an object, like so:

numCol <- testdata$Num
heightCol <- testdata$height
weightCol <- testdata$weight
classCol <- testdata$class

Then, for instance, heightCol gives me

heightCol
> 72.1 75.2 60.3 62.4 50.5

What I need to do is take each class and find the mean vectors, standard deviation, scatter diagrams, and parallel coordinates.

If someone could explain to me how to find, say, just the mean vectors I'm sure I could figure out the rest.

Best Answer

colMeans(testdata)

apply(testdata, 2, mean)

for more details see the helpfiles

?colMeans
?apply

Related Solutions

C++ – How to find out if an item is present in a std::vector

You can use std::find from <algorithm>:

#include <algorithm>
#include <vector>
vector<int> vec; 
//can have other data types instead of int but must same datatype as item 
std::find(vec.begin(), vec.end(), item) != vec.end()

This returns a bool (true if present, false otherwise). With your example:

#include <algorithm>
#include <vector>

if ( std::find(vec.begin(), vec.end(), item) != vec.end() )
   do_this();
else
   do_that();

C++ – How to erase an element from std::vector<> by index

To delete a single element, you could do:

std::vector<int> vec;

vec.push_back(6);
vec.push_back(-17);
vec.push_back(12);

// Deletes the second element (vec[1])
vec.erase(std::next(vec.begin()));

Or, to delete more than one element at once:

// Deletes the second through third elements (vec[1], vec[2])
vec.erase(std::next(vec.begin(), 1), std::next(vec.begin(), 3));

Best Answer

Related Solutions

C++ – How to find out if an item is present in a std::vector

C++ – How to erase an element from std::vector<> by index

Related Topic