[BioC] Heatmap ( )

[Saurin Jani]

Hi,

I am getting very clear blocks of high and low and
medium expression of genes across the heatmap .

I am using :

heatmap(esetMatrix) and using all default values in
them.
  
------|
high  |  low
------|-------|
 low  | high  |
      | (med) |
      |-------|      


Is something wrong I am doing here or heatmaps are
supposed to be 

high low high or low high low


Could anyone explain to me..if possible...please!

thank you,
Saurin