Linear Interpolation of two mismatched matrices

filename='CAL_LID_L2_05kmCPro-Standard-V4-20.2011-12-31T23-18-11ZD_Subset.hdf';
info=hdfinfo(filename);
data=hdfread(filename,'Ice_Water_Content_Profile');             %reading ice water dataset
data1=hdfread(filename,'Latitude');
data(data==-9999)=nan;                                          %removing fill value
data(data<0 | data>0.54)=nan;                                   %removing out of range values
metadata = hdfread(filename, '/metadata', 'Fields', 'Lidar_Data_Altitudes', 'FirstRecord',1 , 'NumRecords',1);
l1_alt=metadata{1};                                             %reading altitude (km)
h=imagesc(rot90(data));                                         %plotting the data
% h=imagesc(data');                                             %plotting the data
set(gca,'YTick',[1:50:399],'YTicklabel',(l1_alt(1:50:399)));
colormap jet
colorbar

The l1_alt is not linearly interpolate with the data. how can i make the l1_alt linearly interpolate so that the increament of altitude (l1_alt) shall increase uniformely with the x-axis?