why this code is used?

function iHelix=snailMatIndex(inMatDims)
if length(inMatDims)==1
inMatDims=repmat(inMatDims, 1, 2);
end
nElemems=inMatDims(1)*inMatDims(2);
indMat =reshape(1:nElemems, inMatDims);
iHelix=[];
while ~isempty(indMat)
if size(indMat, 2)==1
iHelix=cat( 2, iHelix, transpose(indMat(:, 1)) );
indMat=[];
else
iHelix=cat( 2, iHelix, indMat(1, :) );
indMat(1, :)=[]; % remove the current top row
if ~isempty(indMat)

indMat=rot90(indMat); % rotate index matrix 90° clock-
wise

end % if ~isempty(indMat)
end % if size(indMat, 2)==1
end % while ~isempty(indMat)

[Walter Roberson]

Helix scan, I think.

Read the documentation that was provided with the code. If there wasn't any, then ask the author to document the code.