Matlab不解决if语句

Question

I'm having a bit of trouble iterating through a few if statements more than eight times. The code seems to work fine for the first several comparisons, performs the arithmetic and return/saves the output row 'export_data' . However, after that, it only returns the else condition and response. The variables beings assessed have 1500 rows each. I've added the code below and two photos showing the outputs. Any insight will be very much appreciated.

function [export_data] = WS_Zones(Forecast_WS, Observed_WS)
if (Forecast_WS > Observed_WS)
    WS_Zone_1 = Observed_WS.*1.24;
    WS_Zone_2 = Observed_WS.*1.28;
elseif (Forecast_WS < Observed_WS)
    WS_Zone_1 = Observed_WS.*0.76;
    WS_Zone_2 = Observed_WS.*0.72;
else
   WS_Zone_1 = Observed_WS;
   WS_Zone_2 = Observed_WS;
end
export_data=[Forecast_WS Observed_WS WS_Zone_1 WS_Zone_2];
filename = 'testdata.xlsx';
sheet = 1;
xlRange = 'A1';
xlswrite(filename,export_data,sheet,xlRange) 
end

• Expected Output
• Wrong Output

Answer 1

This statement:

if [1 2 3] > [1 1 1]
    disp('hello');
end

will never print "hello" even though 2 and 3 are both greater than 1 . This is because the if statement needs to evaluate to either scalar true or false . If a vector is used, than only the first element is used to determine if the statement is true or not (comparisons between other elements are ignored). You can use any and all if you want to apply conditions on all elements.

If Forecast_WS and Observed_WS aren't scalars then you need to wrap your if statement in a for loop, eg:

WS_Zone_1 = Observed_WS;
WS_Zone_2 = Observed_WS;
for i = 1:numel(Forecast_WS)
    if Forecast_WS(i) > Observed_WS(i)
        WS_Zone_1(i) = Observed_WS(i).*1.24;
        WS_Zone_2(i) = Observed_WS(i).*1.28;
    elseif Forecast_WS(i) < Observed_WS(i)
        WS_Zone_1(i) = Observed_WS(i).*0.76;
        WS_Zone_2(i) = Observed_WS(i).*0.72;
    end
end

or vectorize it using logical indexing :

WS_Zone_1 = Observed_WS;
WS_Zone_2 = Observed_WS;
idx  = (Forecast_WS > Observed_WS);
WS_Zone_1(idx) = Observed_WS(idx).*1.24;
WS_Zone_2(idx) = Observed_WS(idx).*1.28;
idx  = (Forecast_WS < Observed_WS);
WS_Zone_1(idx) = Observed_WS(idx).*0.76;
WS_Zone_2(idx) = Observed_WS(idx).*0.72;