How to generate NDVI from HDF-4 data. (OCM-2 level-1 HDF-4)

Hi,

I have used hdftool, hdfread commands, But my HDF file has only one dataset, then how can i generate NDVI. My matlab commands are given below

hdftool('F:\MATLAB\HDF data\binned hdf\OCMHDFFiles_20-Sep-2012\O2_01APR2011_004_000_GAN_L3B_CL_M.hdf');

Band_3 = hdfread('F:\MATLAB\HDF data\binned hdf\OCMHDFFiles_20-Sep-2012\O2_01APR2011_004_000_GAN_L3B_CL_M.hdf','clo','Fields','?');
Band_2 = hdfread('F:\MATLAB\HDF data\binned hdf\OCMHDFFiles_20-Sep-2012\O2_01APR2011_004_000_GAN_L3B_CL_M.hdf','clo','Fields','?');
Band_1 = hdfread('F:\MATLAB\HDF data\binned hdf\OCMHDFFiles_20-Sep-2012\O2_01APR2011_004_000_GAN_L3B_CL_M.hdf','clo','Fields','?');

% Calculate NDVI.

Band_2 = im2single(Band_2);
Band_3 = im2single(Band_3);
SPCrater_NDVI = (Band_3 - Band_2) ./ (Band_3 + Band_2);

% Display the image.
j=imresize(SPCrater_NDVI,0.5);
figure(5)
% Note that because the range of numbers in our NDVI ratio is between
% 0 and 1, we need to display the image's colors using an appropriate scale
% [0 1]
imshow(j,'DisplayRange',[0 1])

Here my question is indicated by '?' symbol within the codings.

Can anyone please help me to solve this issue.

I really appreciate any help you can provide. I will be grateful if you can send me this information.

M. Prabu

(maprabu)