MapInfo Pro

This is a follow-up article to last week's post of offsetting labels to the left and to the right.

I promised to give you some hints on assigning values in a more automatic way. You can find that in today's article.

Happy #MapInfoMonday!

Assigning Initial Values to the Points

As I said in last week's post, the initial task of assigning values to the points could probably be automated - at least to a certain degree.

Let's look at how you can do this.

For a given dataset, you can use MapBasic to determine the coverage of spatial data. This wil be returned as the minimum and maximum coordinates of the spatial objects.

Set CoordSys Table sTab

fMinLong = TableInfo(sTab, TAB_INFO_MINX)
fMaxLong = TableInfo(sTab, TAB_INFO_MAXX)
fMinLat = TableInfo(sTab, TAB_INFO_MINY)
fMaxLat = TableInfo(sTab, TAB_INFO_MAXY)

When you know the coverage, you can start calculating values to the East and West of the dataset. And you can calculate a middle of the dataset to help you split the dataset into two. These two parts will probably not be of equal size, as that would assume the data is evenly distributed - which it rarely is.

The value fCentLong can help me select points to the left and right of the center of the dataset.

fCentLong = fMaxLong - ((fMaxLong - fMinLong) / 2)

fMinLong = Round(fMinLong, 0.01)
fMaxLong = Round(fMaxLong, 0.01)
fMaxLat = Round(fMaxLat, 0.01)

I can now select the first part of my data, the Western points and calculate value for these.

I select all the records where the CentroidX() of the object is less than or equal to the center value, fCentLong.

I order the result by the Y coordinate so that the labels would appear in this order too.

Select h.LABEL_LONG, h.LABEL_LAT, h.LABEL_POS, CentroidY(h.OBJ) As "LAT"
From sTab As "h"
Where CentroidX(h.OBJ) <= fCentLong
Order By LAT Desc
Into _west NoSelect Hide

Update _west
Set LABEL_POS = "W",
  LABEL_LONG = fMinLong - 0.05,
  LABEL_LAT = fMaxLat - ((ROWID - 1) * 0.05)
Close Table _west

I update the resulting query and set the LABEL_POS to "w", and set the X coordinate of the label point to be placed west of the current data bounds, and finally I calculate the Y coordinate of the labels from the maximum Y coordinate of the data bounds to a lower Y coordinate based on this simple expression:

fMaxLat - ((ROWID - 1) * 0.05)

This value, 0.05, is dependent on your map scale. So you may have to do a bit of trial and error to find the right value.

I do similar calculations for the points that will be moved to the East.

Select h.LABEL_LONG, h.LABEL_LAT, h.LABEL_POS, CentroidY(h.OBJ) As "LAT"
From sTab As "h"
Where CentroidX(h.OBJ) > fCentLong
Order By LAT Desc
Into _east NoSelect Hide

Update _east
Set LABEL_POS = "E",
  LABEL_LONG = fMaxLong + 0.05,
  LABEL_LAT = fMaxLat - ((ROWID - 1) * 0.05)
Close Table _east

After this, I can reuse the script from last week's post to create the label point and label line layers. The new elements of the script look like this:

Dim sTab As String
Dim fMinLong As Float
Dim fMaxLong As Float
Dim fMinLat As Float
Dim fMaxLat As Float
Dim fCentLong As Float

sTab = "Hospitals"
Set CoordSys Table sTab

fMinLong = TableInfo(sTab, TAB_INFO_MINX)
fMaxLong = TableInfo(sTab, TAB_INFO_MAXX)
fMinLat = TableInfo(sTab, TAB_INFO_MINY)
fMaxLat = TableInfo(sTab, TAB_INFO_MAXY)
fCentLong = fMaxLong - ((fMaxLong - fMinLong) / 2)

fMinLong = Round(fMinLong, 0.01)
fMaxLong = Round(fMaxLong, 0.01)
fMaxLat = Round(fMaxLat, 0.01)
 
Select h.LABEL_LONG, h.LABEL_LAT, h.LABEL_POS, CentroidY(h.OBJ) As "LAT"
From sTab As "h"
Where CentroidX(h.OBJ) <= fCentLong
Order By LAT Desc
Into _west NoSelect Hide

Update _west
Set LABEL_POS = "W",
  LABEL_LONG = fMinLong - 0.05,
  LABEL_LAT = fMaxLat - ((ROWID - 1) * 0.05)
Close Table _west

Select h.LABEL_LONG, h.LABEL_LAT, h.LABEL_POS, CentroidY(h.OBJ) As "LAT"
From sTab As "h"
Where CentroidX(h.OBJ) > fCentLong
Order By LAT Desc
Into _east NoSelect Hide

Update _east
Set LABEL_POS = "E",
  LABEL_LONG = fMaxLong + 0.05,
  LABEL_LAT = fMaxLat - ((ROWID - 1) * 0.05)
Close Table _east

Select h.TRADE_NAME, h.*
, CreatePoint(h.LABEL_LONG, h.LABEL_LAT) object
From sTab As "h"
Into _lbl_pnts_all NoSelect

Select * From _lbl_pnts_all
Where LABEL_POS = "W"
Into _lbl_pnts_w NoSelect
Select * From _lbl_pnts_all
Where LABEL_POS = "E"
Into _lbl_pnts_e NoSelect

Add Map Auto Layer _lbl_pnts_w, _lbl_pnts_e
Set Map Layer _lbl_pnts_w Display Global
   Global Symbol (32,16744448,12,"MapInfo Symbols",256,0)
Set Map Layer  _lbl_pnts_e Display Global
   Global Symbol (32,16744448,12,"MapInfo Symbols",256,0)

Select h.*
, CreateLine(CentroidX(h.obj), CentroidY(h.Obj), h.LABEL_LONG, h.LABEL_LAT) object
From sTab As "h"
Into _lbl_lns_all NoSelect

Select * From _lbl_lns_all
Where LABEL_POS = "W"
Into _lbl_lns_w NoSelect

Select * From _lbl_lns_all
Where LABEL_POS = "E"
Into _lbl_lns_e NoSelect

Add Map Auto Layer _lbl_lns_w, _lbl_lns_e
Set Map Layer _lbl_lns_w Display Global Global Line (1,2,16711680)
Set Map Layer _lbl_lns_e Display Global Global Line (1,2,16711680)