A classical N, P, K (nitrogen, phosphate, potassium) factorial
experiment on the growth of peas conducted on 6 blocks. Each half of a
fractional factorial design confounding the NPK interaction was used
on 3 of the plots.
Usage
npk
Format
The npk data frame has 24 rows and 5 columns:
block
which block (label 1 to 6).
N
indicator (0/1) for the application of nitrogen.
P
indicator (0/1) for the application of phosphate.
K
indicator (0/1) for the application of potassium.
yield
Yield of peas, in pounds/plot (the plots were (1/70) acre).
Source
Imperial College, London, M.Sc. exercise sheet.
References
Venables, W. N. and Ripley, B. D. (2002)
Modern Applied Statistics with S. Fourth edition. Springer.
Examples
options(contrasts = c("contr.sum", "contr.poly"))
npk.aov <- aov(yield ~ block + N*P*K, npk)
npk.aov
summary(npk.aov)
coef(npk.aov)
options(contrasts = c("contr.treatment", "contr.poly"))
npk.aov1 <- aov(yield ~ block + N + K, data = npk)
summary.lm(npk.aov1)
se.contrast(npk.aov1, list(N=="0", N=="1"), data = npk)
model.tables(npk.aov1, type = "means", se = TRUE)
Results
R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
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> library(datasets)
> png(filename="/home/ddbj/snapshot/RGM3/R_rel/result/datasets/npk.Rd_%03d_medium.png", width=480, height=480)
> ### Name: npk
> ### Title: Classical N, P, K Factorial Experiment
> ### Aliases: npk
> ### Keywords: datasets
>
> ### ** Examples
> ## No test:
> options(contrasts = c("contr.sum", "contr.poly"))
> npk.aov <- aov(yield ~ block + N*P*K, npk)
> npk.aov
Call:
aov(formula = yield ~ block + N * P * K, data = npk)
Terms:
block N P K N:P N:K P:K
Sum of Squares 343.2950 189.2817 8.4017 95.2017 21.2817 33.1350 0.4817
Deg. of Freedom 5 1 1 1 1 1 1
Residuals
Sum of Squares 185.2867
Deg. of Freedom 12
Residual standard error: 3.929447
1 out of 13 effects not estimable
Estimated effects may be unbalanced
> summary(npk.aov)
Df Sum Sq Mean Sq F value Pr(>F)
block 5 343.3 68.66 4.447 0.01594 *
N 1 189.3 189.28 12.259 0.00437 **
P 1 8.4 8.40 0.544 0.47490
K 1 95.2 95.20 6.166 0.02880 *
N:P 1 21.3 21.28 1.378 0.26317
N:K 1 33.1 33.14 2.146 0.16865
P:K 1 0.5 0.48 0.031 0.86275
Residuals 12 185.3 15.44
---
Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
> coef(npk.aov)
(Intercept) block1 block2 block3 block4 block5
54.8750000 -0.8500000 2.5750000 5.9000000 -4.7500000 -4.3500000
N1 P1 K1 N1:P1 N1:K1 P1:K1
-2.8083333 0.5916667 1.9916667 -0.9416667 -1.1750000 0.1416667
> options(contrasts = c("contr.treatment", "contr.poly"))
> npk.aov1 <- aov(yield ~ block + N + K, data = npk)
> summary.lm(npk.aov1)
Call:
aov(formula = yield ~ block + N + K, data = npk)
Residuals:
Min 1Q Median 3Q Max
-6.4083 -2.1438 0.2042 2.3292 7.0750
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 53.208 2.276 23.381 8.5e-14 ***
block2 3.425 2.787 1.229 0.23690
block3 6.750 2.787 2.422 0.02769 *
block4 -3.900 2.787 -1.399 0.18082
block5 -3.500 2.787 -1.256 0.22723
block6 2.325 2.787 0.834 0.41646
N1 5.617 1.609 3.490 0.00302 **
K1 -3.983 1.609 -2.475 0.02487 *
---
Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
Residual standard error: 3.942 on 16 degrees of freedom
Multiple R-squared: 0.7163, Adjusted R-squared: 0.5922
F-statistic: 5.772 on 7 and 16 DF, p-value: 0.001805
> se.contrast(npk.aov1, list(N=="0", N=="1"), data = npk)
[1] 1.609175
> model.tables(npk.aov1, type = "means", se = TRUE)
Tables of means
Grand mean
54.875
block
block
1 2 3 4 5 6
54.03 57.45 60.77 50.12 50.52 56.35
N
N
0 1
52.07 57.68
K
K
0 1
56.87 52.88
Standard errors for differences of means
block N K
2.787 1.609 1.609
replic. 4 12 12
> ## End(No test)
>
>
>
>
> dev.off()
null device
1
>