Subsetting datasets into a list - r

Question

I am new to R . I've spent hours trying to figure this out and searching Google and SO, but can't seem to find anything that's exactly what I'm looking for. Hopefully you can help?
I have a data set that looks like:
Site(factor) Species Date Mass GDD
1 cockerelli 0017-03-14 2.73 252.1
2 doddsii 0017-01-12 3.73 583.4
4 cockerelli 0017-03-14 2.71 385.4
4 doddsii 0018-05-16 2.22 783.2
1 infrequens 0018-05-16 2.89 583.0
etc.
I split() my data frame into a list of data frames that I can then pass into apply() functions.
splitdata = split(data, paste(data$Species,data$Site))
However, when I use code such as:
grmodel = lapply(splitdata, function(x){
grmodel = aov(x$Mass~x$GDD)
print(summary(grmodel))
})
I get a huge list of ANOVA summaries (like those below), but I don't know which species and site they belong to.
Df Sum Sq Mean Sq F value Pr(>F)
x$GDD 1 0.000022 0.0000216 0.044 0.838
Residuals 9 0.004396 0.0004884
1 observation deleted due to missingness
Df Sum Sq Mean Sq F value Pr(>F)
x$GDD 1 0.0002526 0.0002526 0.65 0.451
Residuals 6 0.0023319 0.0003887
1 observation deleted due to missingness
I was wondering if anyone knows how to alter the code to tell me which species and site the ANOVA table belong to? I've found some answers that talk about paste() and other functions, but nothing I've tried works.
Thanks so much in advance!

Answer 1

As far as I can tell the names should be visible, I'm not sure what you're seeing exactly but maybe a reprex would be useful.
You could also try to use tidy::broom to see clearer:
lapply(split(iris,iris$Species),
function(x) aov(Petal.Length ~ Petal.Width,x))
# $`setosa`
# Call:
# aov(formula = Petal.Length ~ Petal.Width, data = x)
#
# Terms:
# Petal.Width Residuals
# Sum of Squares 0.1625262 1.3152738
# Deg. of Freedom 1 48
#
# Residual standard error: 0.1655341
# Estimated effects may be unbalanced
#
# $versicolor
# Call:
# aov(formula = Petal.Length ~ Petal.Width, data = x)
#
# Terms:
# Petal.Width Residuals
# Sum of Squares 6.695921 4.124079
# Deg. of Freedom 1 48
#
# Residual standard error: 0.2931183
# Estimated effects may be unbalanced
#
# $virginica
# Call:
# aov(formula = Petal.Length ~ Petal.Width, data = x)
#
# Terms:
# Petal.Width Residuals
# Sum of Squares 1.548503 13.376297
# Deg. of Freedom 1 48
#
# Residual standard error: 0.5278947
# Estimated effects may be unbalanced
With tidy::broom :
lapply(split(iris,iris$Species),
function(x) aov(Petal.Length ~ Petal.Width,x) %>% broom::tidy())
# $`setosa`
# term df sumsq meansq statistic p.value
# 1 Petal.Width 1 0.1625262 0.16252620 5.93128 0.01863892
# 2 Residuals 48 1.3152738 0.02740154 NA NA
#
# $versicolor
# term df sumsq meansq statistic p.value
# 1 Petal.Width 1 6.695921 6.69592109 77.93357 1.271916e-11
# 2 Residuals 48 4.124079 0.08591831 NA NA
#
# $virginica
# term df sumsq meansq statistic p.value
# 1 Petal.Width 1 1.548503 1.5485033 5.556707 0.02253577
# 2 Residuals 48 13.376297 0.2786728 NA NA

Answer 2

The names of the result of split are the values of the second argument coerced to character-class and lapply preserves these names, so you should not need to add back any names, but rather just look at:
names(grmodel)
Perhaps you want to do this for output:
for( i in names(grmodel) ){ cat(i);
cat( : : :\n");
print(grmodel[[i]]);
cat("\n\n")}
.... which just prints the names and a bit of spacing for each item in the grmodels list.