-collect stars- does not work with named expressions

[Yehuda Davis]

I'm trying to use a named expression as the values used to attach stars to the coefficients, but I am unable to get it to work.
The values display just fine in the table.
I suspect the issue is that there is some tag that doesn't match, as per this, however, I cannot fathom what tag that would be.

collect stars requires that the attach() result items must have the same tag elements as the p-value result items for the stars labels to show up

MWE below. Stars don't display using p_named, despite the values showing up in the table, but display just fine for _r_p.
My real named expression is more complex, so simply using _r_p would not be a solution.

sysuse auto, replace
collect clear
collect p_named=_r_p: reg mpg weight
collect style cell result, nformat(%6.3fc)
collect stars p_named 0.01 "***" 0.05 "** " 0.1 "*  " 1 "   ", attach(_r_b)
collect layout (colname) (result[_r_b _r_p p_named])
collect stars _r_p 0.01 "***" 0.05 "** " 0.1 "*  " 1 "   ", attach(_r_b)
collect preview

Thank you in advance!

[Andrew Musau]

See

help collect remap

sysuse auto, replace
collect clear
collect p_named=_r_p: reg mpg weight
collect style cell result, nformat(%6.3fc)
collect stars p_named 0.01 "***" 0.05 "** " 0.1 "*  " 1 "   ", attach(_r_b)
collect remap result[_r_p] = result[p_named]
collect layout (colname) (result[_r_b])

Res.:

. collect layout (colname) (result[_r_b])

Collection: default
      Rows: colname
   Columns: result[_r_b]
   Table 1: 2 x 1

---------------------------
              | Coefficient
--------------+------------
Weight (lbs.) |   -0.006***
Intercept     |   39.440***
---------------------------

[Yehuda Davis]

Thank you!
I tried working with remap. But doesn't that simply change the tag on the _r_p results?
As mentioned in my question, I'm trying to do this with results that are not simply _r_p.
For example, suppose I want one-tailed p-values:

sysuse auto, replace
collect clear
collect p_named=(r(table)["pvalue",1...]/2): reg price mpg-foreign
collect style cell result, nformat(%6.3fc)
collect stars p_named 0.01 "***" 0.05 "** " 0.1 "*  " 1 "   ", attach(_r_b)
collect layout (colname) (result[_r_b _r_p p_named])
collect remap result[_r_p] = result[p_named]
collect layout (colname) (result[_r_b])

Res:

. collect layout (colname) (result[_r_b _r_p p_named])

Collection: default
      Rows: colname
   Columns: result[_r_b _r_p p_named]
   Table 1: 11 x 3

----------------------------------------------------
                       | Coefficient p-value p_named
-----------------------+----------------------------
Mileage (mpg)          |     -21.805   0.779   0.390
Repair record 1978     |     184.793   0.580   0.290
Headroom (in.)         |    -635.492   0.102   0.051
Trunk space (cu. ft.)  |      71.499   0.455   0.227
Weight (lbs.)          |       4.521   0.002   0.001
Length (in.)           |     -76.491   0.063   0.032
Turn circle (ft.)      |    -114.278   0.359   0.179
Displacement (cu. in.) |      11.540   0.174   0.087
Gear ratio             |    -318.648   0.778   0.389
Car origin             |    3334.848   0.001   0.000
Intercept              |    9789.494   0.150   0.075
----------------------------------------------------

. 
. collect remap result[_r_p] = result[p_named]
(11 items remapped in collection default)

. 
. collect layout (colname) (result[_r_b])

Collection: default
      Rows: colname
   Columns: result[_r_b]
   Table 1: 11 x 1

------------------------------------
                       | Coefficient
-----------------------+------------
Mileage (mpg)          |  -21.805   
Repair record 1978     |  184.793   
Headroom (in.)         | -635.492   
Trunk space (cu. ft.)  |   71.499   
Weight (lbs.)          |    4.521***
Length (in.)           |  -76.491*  
Turn circle (ft.)      | -114.278   
Displacement (cu. in.) |   11.540   
Gear ratio             | -318.648   
Car origin             | 3334.848***
Intercept              | 9789.494   
------------------------------------

p_named collects one-tailed p-values, and length should then get two stars, but now it's simply overridden by the value from _r_p.
Or am I misuderstanding?

[Yehuda Davis]

My suspicion about non-matching tags being the issue was correct. Named expressions can have different tags than the standard results (specifically, _r_b) that are collected, leading to the stars not being attached.
Some experimentation helped me find which tags were different and enabled me to cobble together this extremely hacky "solution" to make the tags match in this particular case:

sysuse auto, replace
collect clear
collect p_named=(r(table)["pvalue",1...]/2): reg price mpg-foreign

collect style cell result, nformat(%6.3fc)
collect stars p_named 0.01 "***" 0.05 "** " 0.1 "*  " 1 "   ", attach(_r_b)

collect recode program_class nclass = eclass, fortags(result[p_named])
collect addtags coleq[price], fortags(result[p_named])
collect addtags rowname[pvalue], fortags(result[_r_b])

collect layout (colname) (result[_r_b])

Is there a better solution than this?
Jeff Pitblado (StataCorp) I'd love if you could weigh in on this, since you are the one who posted that helpful nugget about collect stars requiring a perfect match of tags.

Thanks!

[Andrew Musau]

Thank you!
I tried working with remap. But doesn't that simply change the tag on the _r_p results?

Correct. In #1, the two sets of p-values coincide. Otherwise, you need to modify the tags as you have shown.

[Yehuda Davis]

Thank you, Andrew!

[Jeff Pitblado (StataCorp)]

Remapping _r_p seems to work, but is not quite the correct solution.

When you use an expression to define a result for collect, that new result gets most of the tag elements you would expect from a copy of the original result, like _r_p's colname and result_type, but the program_class is nclass instead of eclass. This is what is getting in your way. There also may be extra tag elements added to your new result because of the expression used to construct it. In your second example computing "one-tailed" p-values, you have

collect p_named=(r(table)["pvalue",1...]/2): reg price mpg-foreign

So in addition to the usual colname and result_type tag elements, result[p_named] items also get tagged with rowname[pvalue] but not coleq[price].

The simplest solution I can figure here is to also construct your own name for the coefficient results you want the stars to be attached to. Here is how I accomplished this.

sysuse auto, replace
collect clear
* p_named for the "one-tailed" p-values
* b_named for the corresponding coefficients
collect p_named=(r(table)["pvalue",1...]/2) ///
    b_named=(r(table)["b",1...]) ///
    : reg price mpg-foreign
collect style cell result, nformat(%6.3fc)
* label our custom results
collect label levels result ///
    b_named "Coefficient" ///
    p_named "p-value (one-tail)"
* define our stars rules for the results of interest
collect stars _r_p p_named ///
    0.01 "***" 0.05 "** " 0.1 "*  " 1 "   ", ///
    attach(_r_b b_named)
* the stars still did not get attached :(
collect layout (colname) (result[_r_b _r_p b_named p_named])
* we need to force the -rowname- level to agree for our custom results
collect recode rowname pvalue = ignore b = ignore, ///
    fortags(result[p_named b_named])
* now the stars are properly constructed and attached
collect preview

Here is the resulting table.

---------------------------------------------------------------------------
                       | Coefficient p-value Coefficient p-value (one-tail)
-----------------------+---------------------------------------------------
Mileage (mpg)          |  -21.805      0.779  -21.805                 0.390
Repair record 1978     |  184.793      0.580  184.793                 0.290
Headroom (in.)         | -635.492      0.102 -635.492*                0.051
Trunk space (cu. ft.)  |   71.499      0.455   71.499                 0.227
Weight (lbs.)          |    4.521***   0.002    4.521***              0.001
Length (in.)           |  -76.491*     0.063  -76.491**               0.032
Turn circle (ft.)      | -114.278      0.359 -114.278                 0.179
Displacement (cu. in.) |   11.540      0.174   11.540*                0.087
Gear ratio             | -318.648      0.778 -318.648                 0.389
Car origin             | 3334.848***   0.001 3334.848***              0.000
Intercept              | 9789.494      0.150 9789.494*                0.075
---------------------------------------------------------------------------

[Yehuda Davis]

Thank you, Jeff, for the thorough and helpful response!