Hello, found this forum very instructive! I had this doubt of numerical integration in MATLAB. I have to perform this integration in matlab: r = 0:0.01:22.5; //necessary because they automatically become lower and upper limits of integration! theta=0:pi/100:pi; // limits are not to be necessarily these f = 6.09*r*sin(theta); expr = besselj(0,f)*r * (1-0.7.*r); int_ans = trapz(expr,r) // integrating wrt r only..theta must remain like const! now here matrix dimensions are not agreeing! Should i multiply r.*sin(theta) or r*sin(theta) or r' * sin(theta)?? kindly help in this regarding handling num int with multiple variables btw i have to plot the final answer wrt theta!! please help..would be very obliged!