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Last data update: 2014.03.03

R: Calculate confidence intervals for grouped values

CutCI

R Documentation

Calculate confidence intervals for grouped values

Description

CutCI groups values of one variable into intervals with the same number of observations each and computes confidence intervals for the mean of another variable in each interval.

CIrho computes the normal theory confidence interval for a vector of values.

Usage

CutCI(dat, number = 10, func = mean, alpha=0.95)

CIrho(rho, alpha = 0.95)

Arguments

`dat`	a numerical data frame or matrix with two columns, the first of which gets averaged, and the second of which defines the grouping
`number`	the number of equal-count intervals
`func`	summary function for computing the mean
`rho`	a vector of measurements
`alpha`	the desired confidence level

Details

The quantiles for the confidence interval are taken from the standard normal distribution, so a reasonable number of observations per interval would be good.

Value

CutCI returns invisibly a list of length three:

`x`	the midpoints of the grouping intervals
`y`	the means within each interval, as computed by `func`
`yci`	a matrix with two columns, giving the lower and upper end of the confidence interval respectively

CIrho returns a vector of length two, containing the lower and upper end of the confidence interval.

Examples

x = rnorm(100, mean=2)
CIrho(x)

y = 2 + 3*x + rnorm(100)
cc = CutCI(cbind(x,y), number=5)
print(cc)

# Show it
plot(cc$x, cc$y)
arrows(cc$x, cc$yci[,1], cc$x, cc$yci[,2], length=0)

Results


R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
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Type 'license()' or 'licence()' for distribution details.

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Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

> library(maCorrPlot)
Loading required package: lattice
> png(filename="/home/ddbj/snapshot/RGM3/R_BC/result/maCorrPlot/CutCI.Rd_%03d_medium.png", width=480, height=480)
> ### Name: CutCI
> ### Title: Calculate confidence intervals for grouped values
> ### Aliases: CutCI CIrho
> ### Keywords: utilities
> 
> ### ** Examples
> 
> x = rnorm(100, mean=2)
> CIrho(x)
      CL       CU 
1.728857 2.156790 
> 
> y = 2 + 3*x + rnorm(100)
> cc = CutCI(cbind(x,y), number=5)
> print(cc)
$x
[1]  1.790562  6.288306  7.974450  9.972967 13.653822

$y
(-1.68,5.26]  (5.26,7.05]  (7.05,8.72]  (8.72,11.2]  (11.2,16.1] 
   0.3846425    1.3971805    2.0252550    2.5918733    3.3151672 

$yci
                    CL        CU
(-1.68,5.26] 0.1209445 0.6483405
(5.26,7.05]  1.2582086 1.5361525
(7.05,8.72]  1.8995578 2.1509521
(8.72,11.2]  2.3834760 2.8002707
(11.2,16.1]  3.1531429 3.4771915

> 
> # Show it
> plot(cc$x, cc$y)
> arrows(cc$x, cc$yci[,1], cc$x, cc$yci[,2], length=0)
> 
> 
> 
> 
> 
> dev.off()
null device 
          1 
>