[R] Axiom alike formula needs to get prooved
@chw|dom @end|ng |rom gmx@net
Sat Oct 5 23:56:34 CEST 2019
I found the following relationship:
it is given
x is a vector, bm1 and bm2 are vectors of type logical end exactly as long as x
then the following formula returns alwasy TRUE:
all( x[ bm1 & bm2] == x[ bm2][ bm1[ bm2]] )
I think it is no such great deal and a lot of R programmers will know this and use it in their code intutively.
But the point is: Years ago I tried to prove this relationship and found no acceptable solution for that.
Is anyone able to prove this in a mathematical correct way?
Besides that: here is another one
it is given a dataframe 'result_df' with at least the column 'result_value'
best_results <- with( result_df, sort( result_value))[1:100] # lower is better
best_results_bmask <- with( result_df, result_value %in% best_results)
best_results_order2 <- with( result_df[ best_results_bmask, ], order( result_value))
df1 <- result_df[best_results_order, ][ best_results_bmask[best_results_order], ]
df2 <- result_df[best_results_bmask, ][best_results_order2, ]
all( df1 == df2)
# that was the easy part, now this:
df3 <- result_df[best_results_order[ best_results_bmask[ best_results_order]], ]
all( df1 == df3) # it works, but how can I understand that and how it is proven?
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