Error: Invalid parameter/value pair arguments.

Hi there, this code return (Invalid parameter/value pair arguments ) error. Is there any problem with using 'color'? how can I fix it?

clc
clear 
close all
format long g

%% read 
fid = xlsread('WINT.csv');
f = fid(:, 1);
for i = 1:size(north)
    for j=1
        t(i,j)=i;
    end
end

Y = fft(f) ;
dt = mean(diff(t)) ;
fs = 1./(dt*24) ;

L = length(f) ;
ft = fs*(0:L/2)/L ;
P2 = abs(Y/L) ;
P1 = P2(1:L/2+1) ;
P1(2:end-1) = 2*P1(2:end-1) ;
P1 = P1.^2 ;
period = (1./ft)/24 ;
freq = 600 ;

figure

plot(ft*1e9, P1, 'color','b')
xlabel('Frequency [nHz]')
ylabel('PSD')
title('Fourier spectrum')
set(gca, 'XScale', 'log')
xline((1/(freq*24*60*60))*1e9,'color',[125,0,251]/255 , [num2str(freq), ' days'])
set(gca, 'YLim', [0, 40])

Answer 1

[dpb]

" Is there any problem with using 'color'?"

In

xline((1/(freq*24*60*60))*1e9,'color',[125,0,251]/255 , [num2str(freq), ' days'])

yes, there is. The named parameters for xline must follow the last of the input parameters and the second, must be a linespec character or string variable if the third for the label is used. It isn't flexible-enough in parsing inputs to mix up the order. To use a color triplet and the name as an argument, you need to write the above as

xline((1/(freq*24*60*60))*1e9,'-',[num2str(freq),' days'],'color',[125,0,251]/255)

where the linespec is the linestyle '-' character.

One slight difference that makes the name a little simpler could be to use the new(ish) string class that overloads the plus operator--

xline((1/(freq*24*60*60))*1e9,'-',freq+" days",'color',[125,0,251]/255)

NOTA BENE: the use of the " double quotes around the string constant.

[tara es]

Thanks! It work well.