thanks Robert! OK. boxes are atoms withb an empty shape.
I've looked at the docs and can't see where I could read to understand why shape of 1 2 +/ i. 4 is 2 1 and not 1 2 thanks for your help! Chris On 25/09/2014 4:01 PM, "robert therriault" <bobtherria...@mac.com> wrote: > Hi Chris, > > Well there is information on the vocabulary page for Table > http://www.jsoftware.com/help/dictionary/d420.htm > > also Nuvoc has good information on this verb > http://www.jsoftware.com/jwiki/Vocabulary/slash#dyadic > > The actual shape of a box is empty since the box is an atom. In the case > of 1 2 +/ i. 4 the shape is actually 2 4 i.e. 2 rows of 4 not 2 1 > > < 1 2 +/ i. 4 > ┌───────┐ > │1 2 3 4│ > │2 3 4 5│ > └───────┘ > $ < 1 2 +/ i. 4 > $ each < 1 2 +/ i. 4 > ┌───┐ > │2 4│ > └───┘ > > If you wanted the two rows to be in their own boxes then you could do > > ;/ 1 2 +/ i. 4 > ┌───────┬───────┐ > │1 2 3 4│2 3 4 5│ > └───────┴───────┘ > or > > <"1 [ 1 2 +/ i. 4 > ┌───────┬───────┐ > │1 2 3 4│2 3 4 5│ > └───────┴───────┘ > > $ <"1 [ 1 2 +/ i. 4 > 2 > > The above shows that the shape of the two boxes is not actually 1 2 > because each box is an atom the shape is actually just 2. > > You are correct that an understanding of rank and shape is key to getting > J to work for you. If you are looking for information I have always found > Henry Rich's J for C Programmers much more accessible than the J > dictionary. Chapters 5 and 6 are really good at explaining rank and shape > with regard to verbs. http://www.jsoftware.com/help/jforc/contents.htm > > Also, look at Nuvoc on the wiki. This is a crowd sourced resource > organized by Ian Clark and Henry Rich which many have found useful. > http://www.jsoftware.com/jwiki/NuVoc > > Enjoy the ride as you learn J. Welcome aboard. > > Cheers, bob > > > On Sep 24, 2014, at 10:35 PM, Chris Wright <cawright...@gmail.com> wrote: > > > Hi > > > > Could I work out from the docs that > > > > < 1 2 +/ i. 4 > > > > ┌───────┐ > > > > │1 2 3 4│ > > > > │2 3 4 5│ > > > > └───────┘ > > > > will give the above (2 1) shape result > > > > > > and not a (1 2) result like below? > > > > > > ┌───────┬───────┐ > > > > │1 2 3 4│2 3 4 5│ > > > > └───────┴───────┘ > > > > > > > > > > With the (2,1) it's obvious that two 1-cells are returned, and with > (1,2) > > it's not obvious (where is the boundary b/n them), but I wonder if I > could > > have worked out the shape of the output from the docs alone? > > > > > > with thanks > > > > > > Chris > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
