Question: How to run several one-way ANOVAs in R using on different categories?
1
Longshotx 20 wrote:

Thanks for reading my post. I understand how to run non-parametric and parametric tests on three or more groups. But what I haven't figured out was a simple way of doing this multiple times from different categories I am interested in. In my dataset, I have gene copies for various antibiotic classes and I want to see if there are significant differences between samples in each antibiotic class. My data is currently in long format and looks like this:

``````Sample     Class      Value

A       Macrolide  0.22
A       Macrolide  0.45
A       Macrolide  0.63
B       Macrolide  0.25
B       Macrolide  0.28
B       Macrolide  0.47
C       Macrolide  0.22
C       Macrolide  0.26
C       Macrolide  0.29
A       Ceph  0.32
A       Ceph  0.42
A      Ceph  0.62
B       Ceph  0.42
B       Ceph  0.20
B     Ceph  0.91
C       Ceph  0.82
C      MCeph  0.92
``````

So essentially I want to do a one-way ANOVA for Macrolides and then another for Ceph etc etc. Can someone help me?

Thanks

anova statistics R gene • 334 views
modified 8 weeks ago by Neilfws48k • written 3 months ago by Longshotx 20
4
Neilfws48k wrote:

One approach is to `nest` the data in a data frame with a list column. You can then use `purrr::map` to run a function for each group, `tidy` the results and `unnest`.

Using the same `df1` as in the answer from @zx8754:

``````library(dplyr)
library(tidyr)
library(purrr)

df1 %>%
nest(-Class) %>%
mutate(model = map(data, ~anova(lm(Value ~ Sample, .))),
tidy = map(model, tidy)) %>%
select(Class, td) %>%
unnest()
``````

Result:

``````# A tibble: 6 x 7
Class     term         df  sumsq meansq statistic p.value
<chr>     <chr>     <int>  <dbl>  <dbl>     <dbl>   <dbl>
1 Macrolide Sample        2 0.0471 0.0235     1.22    0.358
2 Macrolide Residuals     6 0.115  0.0192    NA      NA
3 Ceph      Sample        2 0.103  0.0515     0.662   0.564
4 Ceph      Residuals     4 0.311  0.0777    NA      NA
5 MCeph     Sample        2 0.161  0.0804     0.447   0.727
6 MCeph     Residuals     1 0.18   0.18      NA      NA
``````

More details: Running a model on separate groups.

Thanks this was extremely helpful!

Hi infenit101,

A small educational note: if an answer was helpful you should upvote it, if the answer resolved your question you should mark it as accepted. (and you can accept multiple answers if need-be) 3

Couldn't you just subset your dataframe for Class. i.e.

``````> library(lmPerm)
> data.df = read.csv("data.txt")

> aov.macro <- lmPerm::aovp(Value ~ Sample, subset(data.df,data.df\$Class == "Macrolide")  )
 "Settings:  unique SS "
> summary(aov.macro)
Component 1 :
Df R Sum Sq R Mean Sq Pr(Exact)
Sample       2 0.047089  0.023544         1
Residuals    6 0.115400  0.019233

> ceph.macro <- lmPerm::aovp(Value ~ Sample, subset(data.df,data.df\$Class == "Ceph")  )
 "Settings:  unique SS "
> summary(ceph.macro)
Component 1 :
Df R Sum Sq R Mean Sq Pr(Exact)
Sample       2  0.10293  0.051467         1
Residuals    4  0.31087  0.077717

> mceph.macro <- lmPerm::aovp(Value ~ Sample, subset(data.df,data.df\$Class == "MCeph")  )
Error in ctrfn(levels(x), contrasts = contrasts) :
not enough degrees of freedom to define contrasts
``````

Not sure if that was intentional but you have one class labelled as MCeph. Seems like a typo, or the data is truncated? If not, you don't have enough degrees of freedom to do an anova on that class (you'd need at least one of each Sample for the function to even work).

1

a small comment, you don't need to write `lmPerm::aovp` since you already loaded the library

Thanks so much! Yes that was a typo.

Can I use the same subsetted dataframe for TukeyHSD?

ADD REPLYlink modified 3 months ago • written 3 months ago by Longshotx 20

Most likely yes. I'm not familiar with the function but it looking at some examples, it looks like it needs takes an input of an anova object (generated by `aov`) so the `lmPerm::aovp` method might not work. Try it, and if it doesn't work use `aov` like in here (with subsetted dataframes):

3
zx87548.2k wrote:

Split data by class, then run your favourite function, see example:

``````# example data
df1 <- read.table(text = "Sample    Class   Value
A   Macrolide   0.22
A   Macrolide   0.45
A   Macrolide   0.63
B   Macrolide   0.25
B   Macrolide   0.28
B   Macrolide   0.47
C   Macrolide   0.22
C   Macrolide   0.26
C   Macrolide   0.29
A   Ceph    0.32
A   Ceph    0.42
A   Ceph    0.62
B   Ceph    0.42
B   Ceph    0.2
B   Ceph    0.91
C   Ceph    0.82
C   MCeph   0.92
A   MCeph   0.2
B   MCeph   0.72
C   MCeph   0.32
", header = TRUE, stringsAsFactors = FALSE)

# split and apply function, result is a named list:
lapply(split(df1, df1\$Class), function(i){
anova(lm(Value ~ Sample, data = i))
})

\$Ceph
Analysis of Variance Table

Response: Value
Df  Sum Sq  Mean Sq F value Pr(>F)
Sample     2 0.10293 0.051467  0.6622 0.5644
Residuals  4 0.31087 0.077717

\$Macrolide
Analysis of Variance Table

Response: Value
Df   Sum Sq  Mean Sq F value Pr(>F)
Sample     2 0.047089 0.023544  1.2241 0.3582
Residuals  6 0.115400 0.019233

\$MCeph
Analysis of Variance Table

Response: Value
Df Sum Sq Mean Sq F value Pr(>F)
Sample     2 0.1608  0.0804  0.4467 0.7268
Residuals  1 0.1800  0.1800
``````