adding function to screen mosaic using mask and assigning NA as well as scaling

initial commit for code generating figures and analyses for NASA Biodiversity conference poster

adding variables to plot RMSE by tiles summary over 30 years

debugging part3, assessment part3 for combining yearly assessment

scaling assessment part3, functions to combine yearly assessment used in stage 8

debugging overall 30 years combination of assessment for region 4, stage 8

running stage 7 mosaicing for region 4 on 1999 for poster NASA biodiversity conference

running overall assessment stage8 30 years summary for region 4, South America

testing code with new flag value and masking file

fixing problem with masking and no data values