feature request: evaluate weights possibly from data

[MatthieuStigler]

Hi

It would be great if argument weights could also be evaluated from the environment of data, not only GLobal Environment, like lm does?

Thanks!

library(lfe)
#> Loading required package: Matrix

lm(freeny.y~lag.quarterly.revenue +price.index, data = freeny, weights = income.level)
#> 
#> Call:
#> lm(formula = freeny.y ~ lag.quarterly.revenue + price.index, 
#>     data = freeny, weights = income.level)
#> 
#> Coefficients:
#>           (Intercept)  lag.quarterly.revenue            price.index  
#>                2.1230                 0.8942                -0.2480
felm(freeny.y~lag.quarterly.revenue +price.index, data = freeny, weights = freeny$income.level)
#>           (Intercept) lag.quarterly.revenue           price.index 
#>                2.1230                0.8942               -0.2480
felm(freeny.y~lag.quarterly.revenue +price.index, data = freeny, weights = income.level)
#> Error in eval(mf[[wpos]], pf): object 'income.level' not found

^{Created on 2019-08-01 by the reprex package (v0.3.0)}