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michaesp |
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function out = int_index (field,indices,mdv)
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% General interpolation routine for data grid
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% Usage: out = int_index(in,index,mdv)
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% Example: out int_index(inp.TH.data,[10.1 20.4 30.3; 23.6 56.7 78.4],mdv)
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% Check whether input data are correct
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if ( length(size(field)) > 3 )
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error('Error in int_index: input field can be at most three-dimensional');
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end
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if ( length(size(indices)) ~= 2 | ...
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length(size(indices)) == 2 & size(indices,2) ~= length(size(field)) )
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error('Input fields for int_index are inconsistent');
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end
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% Get the dimensions of the input field and the indices
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if ( length(size(field)) == 3 )
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nx = size(field,3);
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ny = size(field,2);
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nz = size(field,1);
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xpos = indices(:,3);
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ypos = indices(:,2);
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zpos = indices(:,1);
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elseif ( length(size(field)) == 2 )
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nx = size(field,2);
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ny = size(field,1);
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nz = 1;
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xpos = indices(:,2);
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ypos = indices(:,1);
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zpos = ones(size(xpos));
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end
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% Make the field one-dimensional (needed for vectorised computation)
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field1 = field(:);
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% Get the indices of the neighbouring data points (surrounding grid box)
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ix000 = max(floor(xpos),1);
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iy000 = max(floor(ypos),1);
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iz000 = max(floor(zpos),1);
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ix001 = min(1+floor(xpos),nx);
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iy001 = iy000;
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iz001 = iz000;
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ix010 = ix000;
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iy010 = min(1+floor(ypos),ny);
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iz010 = iz000;
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ix011 = min(1+floor(xpos),nx);
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iy011 = min(1+floor(ypos),ny);
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iz011 = iz000;
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ix100 = ix000;
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iy100 = iy000;
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iz100 = min(1+floor(zpos),nz);
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ix101 = min(1+floor(xpos),nx);
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iy101 = iy000;
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iz101 = min(1+floor(zpos),nz);
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ix110 = ix000;
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iy110 = min(1+floor(ypos),ny);
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iz110 = min(1+floor(zpos),nz);
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ix111 = min(1+floor(xpos),nx);
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iy111 = min(1+floor(ypos),ny);
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iz111 = min(1+floor(zpos),nz);
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% Get the weights for the individual grid points
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fracx = (1-xpos+ix000);
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fracy = (1-ypos+iy000);
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fracz = (1-zpos+iz000);
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frac000 = fracx .* fracy .* fracz ;
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frac001 = (1-fracx) .* fracy .* fracz ;
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frac010 = fracx .* (1-fracy) .* fracz ;
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frac011 = (1-fracx) .* (1-fracy) .* fracz ;
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frac100 = fracx .* fracy .* (1-fracz);
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frac101 = (1-fracx) .* fracy .* (1-fracz);
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frac110 = fracx .* (1-fracy) .* (1-fracz);
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frac111 = (1-fracx) .* (1-fracy) .* (1-fracz);
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% Vectorised interpolation
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out = frac000 .* field1( iz000 + (iy000-1) * nz + (ix000-1) * nz * ny ) + ...
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frac001 .* field1( iz001 + (iy001-1) * nz + (ix001-1) * nz * ny ) + ...
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frac010 .* field1( iz010 + (iy010-1) * nz + (ix010-1) * nz * ny ) + ...
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frac011 .* field1( iz011 + (iy011-1) * nz + (ix011-1) * nz * ny ) + ...
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frac100 .* field1( iz100 + (iy100-1) * nz + (ix100-1) * nz * ny ) + ...
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frac101 .* field1( iz101 + (iy101-1) * nz + (ix101-1) * nz * ny ) + ...
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frac110 .* field1( iz110 + (iy110-1) * nz + (ix110-1) * nz * ny ) + ...
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frac111 .* field1( iz111 + (iy111-1) * nz + (ix111-1) * nz * ny );
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% Handling of missing data values
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mask = ( field1( iz000 + (iy000-1) * nz + (ix000-1) * nz * ny ) == mdv ) | ...
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( field1( iz001 + (iy001-1) * nz + (ix001-1) * nz * ny ) == mdv ) | ...
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( field1( iz010 + (iy010-1) * nz + (ix010-1) * nz * ny ) == mdv ) | ...
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( field1( iz011 + (iy011-1) * nz + (ix011-1) * nz * ny ) == mdv ) | ...
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( field1( iz100 + (iy100-1) * nz + (ix100-1) * nz * ny ) == mdv ) | ...
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( field1( iz101 + (iy101-1) * nz + (ix101-1) * nz * ny ) == mdv ) | ...
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( field1( iz110 + (iy110-1) * nz + (ix110-1) * nz * ny ) == mdv ) | ...
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( field1( iz111 + (iy111-1) * nz + (ix111-1) * nz * ny ) == mdv );
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out(mask) = mdv;
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