Why there is error in using interp2 while assigning loaded data to the variable?

I have a separate struct data file (.mat format) which I need to load and perform interp2.

The struct data file is as in the figure,

The matlab code runs fine while I am using following code

load("H2.mat");

h = interp2(data.P,data.T,data.H,235e+05,315);

But it gives error while using following code

data = load("H2.mat");

h = interp2(data.P,data.T,data.H,235e+05,315);

The error says

Unrecognized field name "P".

Error in hydrogen_enthalpy (line 5)

h = interp2(data.P,data.T,data.H,235e+05,315);

How can this problem be solved?

[Stephen23]

"How can this problem be solved?"

By saving the data in the MAT file as separate arrays, and not stuck inside a scalar structure. This has other benefits too, e.g. the ability to load/replace individual arrays from the MAT file, or accessing them without loading using MATFILE.

Use the -STRUCT option to achieve this. For example:

D.hello = 'blah';
D.world = pi;
save ('test.mat','-struct','D')

Now all of the arrays are saved separately, not in one scalar structure:

whos -file test.mat

  Name       Size            Bytes  Class     Attributes

  hello      1x4                 8  char                
  world      1x1                 8  double              

This means the data can be imported directly into the output structure as you expected:

S = load('test.mat')

S = struct with fields:
    hello: 'blah'
    world: 3.1416

S.hello

ans = 'blah'

S.world

ans = 3.1416

Answer 1

[Voss]

Try this:

S = load("H2.mat");
data = S.data;
h = interp2(data.P,data.T,data.H,235e+05,315);