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the code wont display an answers calculated

조회 수: 2 (최근 30일)
Nasser Ramsis
Nasser Ramsis 2015년 8월 3일
댓글: David Sanchez 2015년 8월 3일
so i have a code that has multiple nested if statements. before calculations are run the user is asked for a method f,b or c and if they choose f and b it works when c is chosen nothing is displayed. but the code seems identical. can anyone help?
function deraproxx %This program will find an approximate solution to the nth order %derrivative of an nth order polynomial where n is 1-4
disp ('Please input a polynomial function') disp ('please use the following format') disp('a*x.^4+b*x.^3+c*x.^2+d*x+e') disp('enter 0 if there is no coefficient to one of the variables') f=input('type now ','s');
disp ('what is the order of derrivation you desire?') n=input('type now ');
disp ('what is the number of terms in taylor series? (1 or 2)') tn=input('type now ');
disp ('what method would you like to use? f, b, or c') method=input('type now ','s');
disp(' what is the step size?') h=input('type now ');
disp('what point would you like to evaluate?') xi=input ('type now ');
x=((xi-5*h):h:(xi+5*h)); y=eval(f);
fxim5=y(1,1); fxim4=y(1,2); fxim3=y(1,3); fxim2=y(1,4); fxim1=y(1,5); fxi=y(1,6); fxip1=y(1,7); fxip2=y(1,8); fxip3=y(1,9); fxip4=y(1,10); fxip5=y(1,11);
if method=='f' if n==1 if tn==1 sna=(fxip1-fxi)/h disp(sna) else sna=(-fxip2+4*fxi+1-3*fxi)/2*h disp(sna) end elseif n==2 if tn==1 sna=(fxip2-2*fxip1+fi)/(h*h) disp(sna) else sna=(-fxip3+4*fxip2-5*fxip1+2*fxi)/(h*h) disp(sna) end elseif n==3 if tn==1 sna=(fxip3-3*fxip2+3*fxip1-fxi)/(h*h*h) disp(sna) else sna=(-3*fxip4+14*fxp3-24*fxip2+18*fxip1-5*fxi)/(2*h*h*h) disp(sna) end else if tn==1 sna=(fxip4-4*fxip3+6*fxp2-4*fxip1-fxi)/(h*h*h*h) disp(sna) else sna=(-2*fxip5+11*fxip4-24*fxip3+26*fxip2-14*fxip1+3*fxi)/(h*h*h*h) disp(sna) end end elseif method=='b' if n==1 if tn==1 sna=(fxi-fxim1)/h disp(sna) else sna=(3*fxi-4*fxim1+fxim2)/2*h disp(sna) end elseif n==2 if tn==1 sna=(fxi-2*fxim1+fxim2)/(h^2) disp(sna) else sna=(2*fxi-5*fxim1+4*fxim2-fxim3)/(h^2) disp(sna) end elseif n==3 if tn==1 sna=(fxi-3*fxim1+3*fxim2-fxim3)/(h^3) disp(sna) else sna=(5*fxi-18*fxim1+24*fxim2-14*fxim3+3*fxim4)/(2*(h^3)) disp(sna) end elseif n==4 if tn==1 sna=(fxi-4*fxim1+6*fxim2-4*fxim3+fxim4)/(h^4) disp(sna) else sna=(3*fxi-14*fxim1+26*fxim2-24*fxim3+11*fxim4-2*fxim5)/(h^4) disp(sna) end else if n==1 if tn==1 sna=(fxip1-fxim1)/(h*2) disp(sna) else sna=(-fxip2+8*fxip1-8*fxim1+fxim2)/(12*h) disp(sna) end elseif n==2 if tn==1 sna=(fxip1-2*fxi_fxim1)/(h*h) disp(sna) else sna=(-fxip2+16*fxip1-30*fxi+16*fxim1-fxim2)/(12*h*h) disp(sna) end elseif n==3 if tn==1 sna=(fxip2-2*fxip1+2*fxim1-fxim2)/(2*h*h*h) disp(sna) else sna=(-fxip3+8*fxip2-13*fxip1+133*fxim1-8*fxim2+fxim3)/(8*h*h*h) disp(sna) end else if tn==1 sna=(fxip2-4*fxip1+6*fxi-4*fxim1+fxim2)/(h*h*h*h) disp(sna) else sna=(-fxip3+12*fxip2-39*fxip1+56*fxi-39*fxim1+12*fxim2-fxim3)/(64*h*h*h*h) disp(sna) end end end end

답변 (1개)

David Sanchez
David Sanchez 2015년 8월 3일
Hi there, after reordering your code, I saw it follows this structure:
method=='f'
--> n= 1,2,3,other_value
method=='b'
--> n=1,2,3,4,other_value -> again an if-statement for n=1,2,3,other_value
you do not have the case for
method=='c'
  댓글 수: 3
David Sanchez
David Sanchez 2015년 8월 3일
it doesn't work the way you did it. Go through your code carefully and you'll find out that you do not have an option when method=='c'
David Sanchez
David Sanchez 2015년 8월 3일
I did it for you. See attached *.m ;)

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