understanding the output of str function in R

Question

I use the str to print out information for a calculate variable

str(samples)
 'mcmc' num [1:1000, 1:228] 0.1079 -0.2367 -0.0757 -0.3414 -0.3382 ...
 - attr(*, "dimnames")=List of 2
  ..$ : NULL
  ..$ : chr [1:228] "B[1,1,1]" "B[2,1,1]" "B[3,1,1]" "B[4,1,1]" ...
 - attr(*, "mcpar")= num [1:3] 20005 25000 5

But how to read these information, or what does this output can tell us? For instance, the third component is attr(*, "mcpar")= num [1:3] 20005 25000 5 , what does it mean?

Answer 1

The attr implies there is an attribute named 'mcpar' which is a numeric vector

attributes(samples)

returns a list of all the attributes of the samples ie it will return dimnames as one attribute and the 'mcpar' as another one

According to documentation

The 'mcpar' attribute of an MCMC object gives the start iteration the end iteration and the thinning interval of the chain.