mjhjmtu

I am trying to use TikZ to produce a staggered rectangular grid in LaTeX: (x,y) with 1<=y<=5 and y<=x<=y+5, say. I have tried the following:

documentclassarticle
usepackagetikz
begindocument
begintikzpicture
foreach y in 1,...,5 
foreach x in y, ...,10 
%%if (x <= y+5) 
draw (x,-y) +(-.5,-.5) rectangle ++(.5,.5);
draw (x,-y) node$a_x^y$;
%%fi


endtikzpicture
enddocument

And this gets me the staggered start. However, if I change the limit of "10" in the second foreach to "y+5", I get an error "! Illegal unit of measure (pt inserted)." If, instead of that, I remove the comment marks and apply an if test, then the diagram is empty. (If I try a simpler "if x < 8", I get the column for x==11, which I do not understand.)

I can easily believe that I haven't got the syntax right -- this is my first attempt at anything in TikZ. So, as well as the simple fix, I would appreciate some meta-advice: How do I debug this? Can you recommend an alternative package where I would not struggle to do such a simple thing? Thanks.

Two reasons why your attempt did not quite give you what you want:

1. You cannot do computations in the argument of foreach.


2. The if clause does not work like that. Since these are integers, you could have worked with ifnum, something like ifnumx<8 or so.

Here is a version that does what I think you want to do.

documentclassarticle
usepackagetikz
begindocument
begintikzpicture
foreach y [evaluate=y as xmax using int(y+5)] in 1,...,5 
foreach x in y, ...,xmax 
draw (x,-y) +(-.5,-.5) rectangle ++(.5,.5);
draw (x,-y) node$a_x^y$;


endtikzpicture
enddocument