conj-rows doesn't work for datasets with different column order about incanter

[davidjameshumphreys]

I tried to look at changing the conj-rows function, but I was unable to alter it without causing more bugs (sel and $ don't return a dataset for just one row).

This function could be used within conj-rows:
(conj-rows
ab-dataset
(reorder-columns ba-dataset [:a :b]))

The conj-rows documentation should be updated to reflect the fact that it has some limitations with respect to column order.

[alexott]

@avishn does this still issue for you?

[alexott]

closed as implemented...

[yubrshen]

@alexott
What's the rational not fixing conj-rows at it's root? It seems to me that it's possible to do so. For example, how about

(defn conj-rows
  "Returns a dataset created by combining the rows of the given datasets   and/or collections.
   Examples:
     (use '(incanter core datasets))
     (def cars (get-dataset :cars))
     (view (conj-rows (to-dataset (range 5)) (to-dataset (range 5 10))))
     (view (conj-rows cars cars))
     (view (conj-rows [[1 2] [3 4]] [[5 6] [7 8]]))
     (view (conj-rows [{:a 1 :b 2} {:a 3 :b 4}] [[5 6] [7 8]]))
     (view (conj-rows (to-dataset [{:a 1 :b 2} {:a 3 :b 4}]) [[5 6] [7 8]]))
     (conj-rows (range 5) (range 5 10))
"
  ([& args]
     (reduce (fn [A B]
               (let [a (to-dataset A :transpose true)
                     the-column-names (:column-names a)
                     b (reorder-columns (to-dataset B :transpose true) the-column-names)]
                 (dataset the-column-names
                          (concat (to-list a) (to-list b)))))
             args)))

I wasted several hours to track down to conj-rows' peculiar behavior, by looking at the source code.

Fixing conj-rows' documentation would be helpful, but I wish to remove the burden to user as much as possible. This is a typical incidental complexity, that the user should not bear, if possible.

If you think that there is no negative impact, I can take care of the regression test for the fix. (This is how I fix it for my application.)

Thanks,

Yu