matlab中出现 Undefined function or method 'plus' for input arguments of type 'cell'.怎么解决?

clc;clear; x=1:1:63; y=(3000/2 * (1-cos(3*pi*(x + 5/3) /20)).*( x<5 ))+... ((3000).*(x>5&x<56))+... (3000/2 * (1-cos(-3*pi*(x - 20/3-56) /20))).*(x>56&x<61)+... (450.*(x>61)); plot(x,y) semilogy(x,y)