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我用一个调用函数来计算一个区间上的函数值并画图。此调用函数的输出是x = [x1; x2; x3];我想要把三个值的图像都画出来,编写的plot语句却都错了。错误信息:! g% `" i$ L3 |' _$ j6 [7 o q
错误使用 plot。7 } W& X& c8 C% P4 E
数据必须为可转换为双精度值的数值、日期时间、持续时间或数组。; |* o( M6 \. n0 R7 }, T
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出错 Untitled3 (line 3)$ Y: b9 G" V! K$ [
plot(y,c(:,1));7 j& T" ^: U8 m; U7 C6 ]8 K
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以下是程序,使用的64位R2018。
' t/ O. @( E! Oy=9.9:0.01:10.1;9 h- V' G2 u- Y- @; ]1 h
c=Solve3Polynomial(1,2.*k-20,power(k-10,2)+0.00005,-0.000001);% R& D: g" S& i' R4 C' e) W6 Z, t
plot(y,c(:,1));
# ^" Q, z! n( V O; ]1 [9 \, ^plot(y,c(:,2));
$ t+ |# H/ P! t0 l% Cplot(y,c(:,3));
# [" }' `% D# O3 f! z( Sfunction x = Solve3Polynomial(a,b,c,d)
7 e; v% s; n8 O9 c3 r7 l% 范盛金. 一元三次方程的新求根公式与新判别法[J]. 海南师范学院学报,1989,2(2):91-98.
Q5 i; K( y- A [ R. K0 hsyms x1 x2 x3;" j7 d- x$ P' U6 d" }' w) p
A = b.*b - 3.*a.*c; if abs(A) < 1e-14; A = 0; end
, _5 ]& x H! O/ EB = b.*c - 9.*a.*d; if abs(B) < 1e-14; B = 0; end
) ~7 U4 ?- j" b8 l- _/ B$ uC = c.*c - 3.*b.*d; if abs(C) < 1e-14; C = 0; end 9 ]- D6 d5 X* |/ o0 s9 x+ W3 l, v% N+ C
DET = B.*B - 4.*A.*C; if abs(DET) < 1e-14; DET = 0; end
4 I# o5 D8 V0 P& K4 \if (A==0)&(B==0)4 n! V7 L9 Z4 y. }* w$ W- b1 M
x1 = -c./b; x2 = x1 ; x3 = x1;# `& D+ Q- g4 L s; @7 W
end* b4 T' ^& E" R) K4 M( [
if DET > 0
" h% [5 X! @" `6 ? Y1 = A.*b + 1.5.*a.*(-B + sqrt(DET));- k K+ S8 F5 m7 x
Y2 = A.*b + 1.5.*a.*(-B - sqrt(DET));
" F- a5 L. M' z) Y( y2 H% N2 O, p y1 = nthroot(Y1,3); y2 = nthroot(Y2,3);
1 s& P& K6 i% H4 R/ {' k' P0 L x1 = (-b-y1-y2)./(3.*a);1 v# ^4 y" m6 r
vec1 = (-b + 0.5.*(y1 + y2))./(3.*a); 5 o2 P6 J: `2 @5 h
vec2 = 0.5.*sqrt(3).*(y1 - y2)./(3.*a);2 Z3 D2 N7 j% p: q. ]
x2 = 0;( @* n Q& m5 ?+ f
x3 = 0;& c) F8 b& T" Z% \, O3 m
clear Y1 Y2 y1 y2 vec1 vec2;2 f! H/ o, P2 O; b2 Y2 {6 ?$ _ W
end
! a6 m# u0 \# @3 j) Q, [+ W- Lif DET == 0 & (A ~= 0) & (B ~= 0)5 ~1 L9 D% w2 c6 ]4 s4 P
K = (b.*c-9.*a.*d)./(b.*b - 3.*a.*c); K = round(K,14);
7 B4 j# `! h- @- ?7 T" V! X, X x1 = -b./a + K; x2 = -0.5.*K; x3 = x2;
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if DET < 0
; b% v( D" ?9 d3 H sqA = sqrt(A);4 @- C; A2 T1 @, O# D2 ~
T = (A.*b - 1.5.*a.*B)./(A.*sqA);; [+ t" h; l$ y4 T7 J, [
theta = acos(T); [2 ]. r" M' s: y
csth = cos(theta./3);
5 Y( H. \/ a1 A sn3th = sqrt(3).*sin(theta./3);8 J ~% O2 r) c0 x5 X3 h$ h
x1 = (-b - 2.*sqA.*csth)./(3.*a);
& B- i; @( e9 z6 }( W9 B6 d) n x2 = (-b + sqA.*(csth + sn3th))./(3.*a);
" h2 y. C- O" B( V1 p x3 = (-b + sqA.*(csth - sn3th))./(3.*a);
- A) O \, @* V6 X1 l clear sqA T theta csth sn3th;% o' `8 g6 r s9 P* S* u, ^
end
9 Y* {) ` e' U6 |8 ux = [x1; x2; x3];' K- ^' R0 n6 |2 W" a0 U$ L6 E1 ?4 \
end, o) }$ l6 h6 Z" P+ A! L% d# L
; _/ u( t- E3 }. u6 R0 j' k麻烦大神帮忙指点一下,非常感谢! |
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