I am trying to map a dataset with associated latitude and longitude. The details of the data I am using are given below:

```
Variable   Type       Data/Info
-------------------------------
lat    ndarray    1826x960, type `float64`
lon    ndarray    1826x960, type `float64`
data   ndarray    1826x960, type `float64`

```

I have created then a basemap:

```
m = Basemap(projection='cyl', llcrnrlon=-180, urcrnrlon=180, llcrnrlat=-40, urcrnrlat=40, resolution='c')

```

Now, on the basemap created, I'd plot the above mentioned dataset using pcolormesh:

```
m.drawcoastlines()
m.drawcountries
x,y = m(lon,lat)
m.pcolormesh(x,y,data)
m.colorbar()
plt.show()

```

This gives following figure:
[Temp Brightness plot](http://i.stack.imgur.com/W5LNF.png)

But if I perform similar plot on a dataset (size 2691x960, same goes to lon and lat) covering whole londitude stretch(-180 to 180), I get a 'strange bar':
[strange bar](http://i.stack.imgur.com/vj47g.png)

I am pretty sure that the strange bar occurs due to the overlapping of dataset. The same plot has been performed in matlab and it works pretty fine. 

Please tell me what the problem is, what can be done to remove the bar, what are the other methods of plotting this kind of data in python.