Commands, Functions,

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Commands, Functions, GRID Algebra

• FE423 - January 11, 2000

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Outline

• Commands vs. Functions
• GRID Algebra
• LOCAL, FOCAL, and ZONAL functions

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Commands vs. Functions

• Commands
• command ltingridgt ltoutgridgt
• Functions
• ltoutgridgt function(ltingridgt)

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Examples of Commands

• copy g/fe423/dem dem
• fill dem filled_dem
• linegrid roads roadgrid
• histogram dem

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Examples of Functions

• slope slope(dem, degree)
• temp base_temp lapse dem
• roadgrid linegrid(roads)
• shade hillshade(dem)

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GRID Function Types

• Arithmatic - /
• outgrid grid1 grid2 grid3
• Math functions
• log(), sin(), pow(g1,g2), max(g1,g2)
• Logical
• newdem con(dem gt 0, dem, 0)

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GRID Algebra

• Precedence
• outgrid grid1 grid2 grid3
• Nesting functions within functions
• outgrid log(grid1 sin(pow(grid2,grid3)))
• Spacing or ( or ,
• before and after each function and grids

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LOCAL, FOCAL, and ZONAL

• LOCAL
• everything so far
• FOCAL
• focussed around a point
• ZONAL
• in that same zone