# How to multiply raster DEM with a linear graph value

I would like to multiply my Raster DEM with a linear graph value y = mx + C. The graph values look as follows:

I want to make a new raster where each cell will represent a damage factor from above graph and by taking into account corresponding cell DEM value. It means, if any particular cell in my DEM raster has a elevation value 10 m, then in my new computed raster this will be damage factor 1. Similarly, any cell of DEM raster has a value of 20 m, the computed new value will be 3 as shown in the graph.

I am familiar with the approach called 'Reclassify'. But reclassify requires a certain range of value, for example elevation 10 - 20 m will be damage factor 1.5.

I want to compute every pixel of DEM raster and redefine it in the form of damage factor by following the linear equation.

Can I write an equation such as y = m*x + c in raster calculator in Qgis /Grass /ArcGIS?

• The figure actually is nonlinear: look at the strange spacings on the y-axis. Although the graph when plotted on this axis is indeed a line, the function describing the damage factor for each elevation is not. Oct 29, 2013 at 13:39