ncexists: 2-10x speedup, scalar variable

Author: scivision

+stdlib/+hdf5nc/ncexists.m

@@ -1,11 +1,19 @@
-function exists = ncexists(file, vars)
+function exists = ncexists(file, variable)
 
 arguments
   file (1,1) string {mustBeFile}
-  vars string
+  variable string {mustBeScalarOrEmpty}
 end
 
-% NOT contains because we want exact string match
-exists = ismember(vars, stdlib.hdf5nc.ncvariables(file));
+exists = false;
+
+try
+  ncinfo(file, variable);
+  exists = true;
+catch e
+  if ~any(contains(e.identifier, ["MATLAB:imagesci:netcdf:badLocationString", "MATLAB:imagesci:netcdf:unknownLocation"]))
+    rethrow(e)
+  end
+end
 
 end

+stdlib/h5exists.m

@@ -1,6 +1,6 @@
 function exists = h5exists(file, variable)
-%% H5EXISTS(file, vars)
-% check if object(s) exists in HDF5 file
+%% H5EXISTS(file, variable)
+% check if object exists in HDF5 file
 %
 %%% Inputs
 % * file: data filename
@@ -10,8 +10,8 @@
 % * exists: boolean
 
 arguments
-    file (1,1) string {mustBeFile}
-    variable string {mustBeScalarOrEmpty}
+  file (1,1) string
+  variable string {mustBeScalarOrEmpty}
 end
 
 exists = stdlib.hdf5nc.h5exists(file, variable);

+stdlib/ncexists.m

@@ -1,19 +1,19 @@
-function exists = ncexists(file, vars)
-%% ncexists(file, vars)
-% check if variable(s) exists in NetCDF4 file
+function exists = ncexists(file, variable)
+%% ncexists(file, variable)
+% check if variable exists in NetCDF4 file
 %
 %%% Inputs
 % * file: data filename
-% * varname: path(s) of variable in file
+% * variable: path of variable in file
 %
 %%% Outputs
-% * exists: boolean (scalar or vector)
+% * exists: boolean
 
 arguments
-  file (1,1) string {mustBeFile}
-  vars string
+  file (1,1) string
+  variable string {mustBeScalarOrEmpty}
 end
 
-exists = stdlib.hdf5nc.ncexists(file, vars);
+exists = stdlib.hdf5nc.ncexists(file, variable);
 
 end

test/TestNetCDF.m

@@ -90,19 +90,14 @@ function test_exists(tc)
 import matlab.unittest.constraints.IsScalar
 basic = tc.TestData.basic;
 
-tc.verifyEmpty(stdlib.ncexists(basic, string.empty))
-
 e = stdlib.ncexists(basic, "");
 
 tc.verifyThat(e, IsScalar)
 tc.verifyFalse(e)
 
-e = stdlib.ncexists(basic, ["A1", "oops"]);
-tc.verifyTrue(isvector(e))
-tc.verifyEqual(e, [true, false])
+tc.verifyTrue(stdlib.ncexists(basic, "A1"))
+tc.verifyFalse(stdlib.ncexists(basic, "not-exist"))
 
-e = stdlib.ncexists(basic, {'A0', 'A1', 'A2', 'A3', 'A4'});
-tc.verifyTrue(all(e))
 end