Loads: mler_coefficients phase calculation has wrong sign (negative instead of positive)

[simmsa]

The test_mler_coefficients() test fails because many of the calculated phase values are negative when the validation data expects positive values. The calculated values are close to the negative of expected values.

MHKiT-MATLAB/mhkit/tests/Loads_TestExtreme.m

Lines 5 to 25 in 31388bb

	function test_mler_coefficients(testCase)
	% `mler_coefficients` Line 54, 55
	% phase delay should be positive number
	% phase = -unwrap(angle(RAO));
	% Per @simmsa, this does not perform this conversion correctly for positive RAO values
	assumeFail(testCase, "Per @simmsa, ask @hivanov about setting RAO to negative values per the above comment");
	% create inputs and load validation data
	fpath = '../../examples/data/loads/mler.csv';
	validation = readtable(fpath);
	wave_freq = linspace(0,1,500);
	js = jonswap_spectrum(wave_freq,15.1,9);
	response_desired = 1;
	RAO = validation.RAO;
	RAO = RAO';
	% execute function
	mler = mler_coefficients(RAO, js, response_desired);
	% assertions
	assertEqual(testCase, mler.conditioned_spectrum, validation.Res_Spec', 'RelTol',0.005)
	assertEqual(testCase, mler.phase, validation.phase', 'RelTol',0.001)
	end

================================================================================
Assertion failed in Loads_TestExtreme/test_mler_coefficients and it did not run to completion.
    ---------------------
    Framework Diagnostic:
    ---------------------
    assertEqual failed.
    --> The numeric values are not equal using "isequaln".
    --> The error was not within relative tolerance.
    --> Failure table (First 50 out of 499 failed indices):
            Index           Actual              Expected              Error              RelativeError      RelativeTolerance
            _____    _____________________    ____________    _____________________    _________________    _________________
                                                                                                                             
             2       -0.000224700554874433    0.000224701     -0.000449401554874433    -1.99999801903166          0.001      
             3       -0.000392122769765216    0.000392123     -0.000784245769765216    -1.9999994128506           0.001      
             4       -0.000510693802738911    0.000510694     -0.00102138780273891     -1.99999961373917          0.001      
             5       -0.000588840811862077    0.000588841     -0.00117768181186208     -1.99999968049453          0.001      
             6       -0.000634990955201273    0.000634991     -0.00126998195520127     -1.99999992944982          0.001      
             7       -0.000657571390823059    0.000657571     -0.00131514239082306     -2.00000059434351          0.001      
             8       -0.000665009276793997    0.000665009     -0.001330018276794       -2.00000041622594          0.001      
             9       -0.0008200481728313      0.000820048     -0.0016400961728313      -2.00000021075754          0.001      
             10      -0.000949085850235464    0.000949086     -0.00189817185023546     -1.9999998422013           0.001      
             11      -0.00123230328236302     0.001232303     -0.00246460628236302     -2.00000022913441          0.001      
             12      -0.00140189792379037     0.001401898     -0.00280379592379037     -1.99999994563825          0.001      
             13      -0.00176849289306414     0.001768493     -0.00353698589306414     -1.99999993953278          0.001      
             14      -0.00203051807713144     0.002030518     -0.00406103607713144     -2.00000003798609          0.001      
             15      -0.00237729200152515     0.002377292     -0.00475458400152515     -2.00000000064155          0.001      
             16      -0.00271359768181828     0.002713598     -0.00542719568181828     -1.99999988274545          0.001      
             17      -0.00317708975498676     0.00317709      -0.00635417975498676     -1.99999992288124          0.001      
             18      -0.00364240991212135     0.00364241      -0.00728481991212135     -1.99999997587349          0.001      
             19      -0.00409416804062982     0.004094168     -0.00818833604062982     -2.00000000992383          0.001      
             20      -0.00462856220868233     0.004628562     -0.00925712420868233     -2.00000004508578          0.001      
             21      -0.00524423530485101     0.005244235     -0.010488470304851       -2.00000005813069          0.001      
             22      -0.00582594818784345     0.005825948     -0.0116518961878434      -2.00000003224255          0.001      
             23      -0.00652650634900939     0.006526506     -0.0130530123490094      -2.00000005347569          0.001      
             24      -0.00729889889043891     0.007298899     -0.0145977978904389      -1.99999998498937          0.001      
             25      -0.00804282248243862     0.008042822     -0.0160856444824386      -2.00000005998375          0.001      
             26      -0.00890869652455034     0.008908697     -0.0178173935245503      -1.99999994663084          0.001      
             27      -0.00975469790383186     0.009754698     -0.0195093959038319      -1.99999999014135          0.001      
             28      -0.0108416905059598      0.010841691     -0.0216833815059598      -1.99999995443145          0.001      
             29      -0.0119015396045846      0.01190154      -0.0238030796045846      -1.99999996677612          0.001      
             30      -0.0130175610264211      0.013017561     -0.0260351220264211      -2.00000000202965          0.001      
             31      -0.0143657642252843      0.014365764     -0.0287315282252843      -2.00000001568202          0.001      
             32      -0.015809314806658       0.015809315     -0.031618629806658       -1.99999998777038          0.001      
             33      0.000327255899107794     -0.000327256    0.000654511899107794     -1.9999996917025           0.001      
             34      -0.00131181308575236     0.001311813     -0.00262362608575236     -2.00000006536934          0.001      
             35      -0.00300742308808337     0.003007423     -0.00601484608808337     -2.00000002928865          0.001      
             36      -0.00486593209829286     0.004865932     -0.00973186409829286     -2.00000002020021          0.001      
             37      -0.00676562681836096     0.006765627     -0.013531253818361       -1.99999997315267          0.001      
             38      -0.00883430728825634     0.008834307     -0.0176686142882563      -2.0000000326292           0.001      
             39      -0.0110710580870874      0.011071058     -0.0221421160870874      -2.00000000786623          0.001      
             40      -0.0136638180606867      0.013663818     -0.0273276360606867      -2.00000000444142          0.001      
             41      -0.0164779929983223      0.016477993     -0.0329559859983223      -1.99999999989819          0.001      
             42      -0.0198617790133211      0.019861779     -0.0397235580133211      -2.00000000067069          0.001      
             43      -0.0183842079438225      0.018384208     -0.0367684159438225      -1.99999999694425          0.001      
             44      -0.00820642596506204     0.008206426     -0.016412851965062       -1.99999999574261          0.001      
             45      -0.0111181003409486      0.0111181       -0.0222362003409486      -2.00000003066608          0.001      
             46      -0.0151693577848328      0.015169358     -0.0303387157848328      -1.99999998581567          0.001      
             47      -0.0190479368817326      0.019047937     -0.0380958738817326      -1.99999999379107          0.001      
             48      -0.0239555725950801      0.023955573     -0.0479111455950801      -1.99999998309705          0.001      
             49      -0.0272588003963284      0.0272588       -0.0545176003963284      -2.00000001453947          0.001      
             50      -0.0225127037982987      0.022512704     -0.0450254077982987      -1.99999999104056          0.001      
             51      -0.0186421827867802      0.018642183     -0.0372843657867802      -1.99999998856251          0.001      
    
    Actual Value:
        1x500 double
    Expected Value:
        1x500 double

@hivanov-nrel, the sign appears to be flipped here:

MHKiT-MATLAB/mhkit/loads/extreme/mler_coefficients.m

Lines 54 to 55 in 31388bb

	% phase delay should be positive number
	phase = -unwrap(angle(RAO));

Should the calculation be phase = unwrap(angle(RAO)); which would produce positive values? When I remove the negative sign the tests pass.

[simmsa]

Closing, fixed by @hivanov-nrel in #179. Will be included in the next release.