[R] couple of how-to-do it in R questions regarding corelations and mean and SD of likert items

Tue Mar 6 15:10:48 CET 2018

Your quickest way to learn about R is to use the manual pages that are included with your installation. Typing the command ?cor produces a page with the following information:

x 	a numeric vector, *matrix* or *data frame*.
y 	NULL (default) or a vector, *matrix* or *data frame* with compatible dimensions to x. The default is equivalent to y = x (but more efficient).

In other words cor(x, y) gives you the correlations between x (rows) and y (columns). 

Descriptive statistics can be found in many packages and each organizes the material differently. In addition to aggregate() which makes it possible to put multiple variables on a single row, you might look at numSummary() in package RcmdrMisc if you want a single variable on each row:

library(RcmdrMisc)
data(iris)
options(digits=3)
numSummary(iris[, 1:4], statistics=c("mean", "sd"))
             mean    sd   n
Sepal.Length 5.84 0.828 150
Sepal.Width  3.06 0.436 150
Petal.Length 3.76 1.765 150
Petal.Width  1.20 0.762 150

numSummary(iris[, 1:4], statistics=c("mean", "sd"), groups=iris$Species)

Variable: Sepal.Length 
           mean    sd  n
setosa     5.01 0.352 50
versicolor 5.94 0.516 50
virginica  6.59 0.636 50

Variable: Sepal.Width 
           mean    sd  n
setosa     3.43 0.379 50
versicolor 2.77 0.314 50
virginica  2.97 0.322 50

Variable: Petal.Length 
           mean    sd  n
setosa     1.46 0.174 50
versicolor 4.26 0.470 50
virginica  5.55 0.552 50

Variable: Petal.Width 
            mean    sd  n
setosa     0.246 0.105 50
versicolor 1.326 0.198 50
virginica  2.026 0.275 50

---------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77843-4352

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of PIKAL Petr
Sent: Tuesday, March 6, 2018 7:10 AM
To: faiz rasool <faiz7r at gmail.com>; r-help at r-project.org
Subject: Re: [R] couple of how-to-do it in R questions regarding corelations and mean and SD of likert items

Hi

For first question, maybe I am completely wrong but

cor(swiss[,-1], swiss[,1])

should give you what you want in one step.

Second question

Without an example it is hard to say but maybe aggregate is the way forward.

> aggregate(iris[,1:4], list(iris$Species), function (x) c(mean=mean(x), 
> sd=sd(x)))
     Group.1 Sepal.Length.mean Sepal.Length.sd Sepal.Width.mean Sepal.Width.sd
1     setosa         5.0060000       0.3524897        3.4280000      0.3790644
2 versicolor         5.9360000       0.5161711        2.7700000      0.3137983
3  virginica         6.5880000       0.6358796        2.9740000      0.3224966

Cheers
Petr

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of faiz 
> rasool
> Sent: Tuesday, March 6, 2018 1:04 PM
> To: r-help at r-project.org
> Subject: [R] couple of how-to-do it in R questions regarding 
> corelations and mean and SD of likert items
>
> Dear list, I have the following how-to-do it in R, questions.
>
> Suppose I have ten independent variables, and one dependent variable.
> I want to find the Pearson correlation of all the IVs with the DV, but 
> not the correlation between the IVs.
>
> What I know so far, about R, that I have to type the cor () function 
> ten times, each time requesting for a correlation between one IV and the DV.
>
> I was wondering that is there a way that I can accomplish what I want 
> with a single function or a fewer line of codes.
>
> My final goal is to create a table in Microsoft word comprising of ten 
> rows, each row for each independent variable and its correlation with the DV.
>
> Based on what I know, I’ll be typing cor (IV,,DV), ten times, and then 
> typing the values in the table in MS  Word.
>
>
> Secondly, I  would like to create a table that provides the details of 
> means and standard deviations, of multiple variables.
>
> The variables are  ratings scores of  likert  type items. What I’d 
> like to do is to construct a table, where each row has the question, 
> its mean and standard deviation. I know that using the psych package, 
> I can have the mean of each item in the scale, but, how to develop a 
> table that has the item, mean, and SD on a same row? I do not know.
>
> Thank you for reading my questions.
>
> Regards,
> Faiz.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see 
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

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