Getting variables names from glmnet lasso into a data.frame

Question

I'm working with a phyloseq object ps.scale and trying to get the most important variables/features that can predict health status sample_data(ps.scale)$group.

Code is as follows:

library(glmnet)

metadata <- factor(sample_data(ps.scale)$group)

otu_tab <- otu_table(ps.scale)
otu_tab <- apply(otu_tab, 2, function(x) x+1/sum(x+1))
otu_tab <- t(log10(otu_tab))

y <- metadata
x <- otu_tab

lasso <- cv.glmnet(x, y, family="multinomial", alpha=1)
print(lasso)
plot(lasso)

So I get the results and a plot here.

#Call:  cv.glmnet(x = x, y = y, family = "multinomial", alpha = 1) 

#Measure: Multinomial Deviance 

#     Lambda Index Measure      SE Nonzero
#min 0.03473    36   1.704 0.05392      68
#1se 0.05529    26   1.751 0.05474      16

Now I want to be able to extract the important variables/features (i.e., OTUs). Below are some codes I gathered from the internet:

Code 1

all_1se <- coef(lasso, s = "lambda.1se")
chosen_1se <- all_1se[all_1se > 0, ]
chosen_1se

#Error: 'list' object cannot be coerced to type 'double'

Code 2

tmp_coeffs <- coef(lasso, s = "lambda.1se")
data.frame(name = tmp_coeffs@Dimnames[[1]][tmp_coeffs@i + 1], coefficient = tmp_coeffs@x)

#Error in data.frame(name = tmp_coeffs@Dimnames[[1]][tmp_coeffs@i + 1],  : 
#  trying to get slot "Dimnames" from an object of a basic class ("list") with no slots

Code 3

myCoefs <- coef(lasso, s="lambda.min");
myCoefs[which(myCoefs != 0 ) ] 

myCoefs@Dimnames[[1]][which(myCoefs != 0 ) ] #feature names: intercept included

## Asseble into a data.frame
myResults <- data.frame(
  features = myCoefs@Dimnames[[1]][ which(myCoefs != 0 ) ], #intercept included
  coefs    = myCoefs              [ which(myCoefs != 0 ) ]  #intercept included
)
myResults

#Error in h(simpleError(msg, call)) : 
error in evaluating the argument 'x' in selecting a method for function 'which': 'list' object cannot be coerced to type 'double'
#3.h(simpleError(msg, call))
#2..handleSimpleError(function (cond) 
#  .Internal(C_tryCatchHelper(addr, 1L, cond)), "'list' object cannot be coerced to type 'double'", 
#  base::quote(which(myCoefs != 0)))
#1.which(myCoefs != 0)

I need help fixing the above errors, mainly 'list' object cannot be coerced to type 'double'.

Thank you in advance.