尝试实现绘图功能，但不显示图表

Posted 2023-02-17

【中文标题】尝试实现绘图功能，但不显示图表

【英文标题】：Trying implement the plot function but its not displaying the graph

【发布时间】：2016-08-30 02:37:21

【问题描述】：

在这个 MATLAB 代码中，我打算显示一个图形，但它显示的是一个空图形。

% Proposed Model For Two-Phase Flow Analytical Design Equation for gas
% pipelines
clc
d = 26.75; % diameter in inches 
pie = 3.142; %normal pie
A = (pie *d^2)/4; % Compute for the area
qm = 150; %volume flow rate of mixture
pm = 8; %Density of the mixture
Wm = qm* pm; % mass flow rate of mixture i.e oil and gas
Ho = 0.01; %Liquid Hold up
z = 0.85; % compressibility factor
R = 10.73; % Gas constant 
f = 0.0254; %friction factor
p0 = 150; % Density of oil
T = 580; % Temperature in R degrees
P0 =1700; % 1700psi
L = 63.068; % Length
P1 = 602.7; % 602.7 psia
%Assume
Mg = 9.8;

formule1 = d*A^2*Mg*(1-Ho);
formule2 = f*Wm^2*z*R*T;
formule = formule1/formule2;
exprs1 = (p0*Ho*z*R*T)/Mg*(1-Ho);
express2 = P2^2-P1^2
drop_p =P1-P2
express3 = 2*p0*Ho*z*R*T*drop_p
better_express = express2 + express3
func1 = d/f

solve( (formule*better_express)- func1*log(P2+ exprs1/P1 + exprs1)^2 + L == 0, P2)
figure
plot(drop_p,L,'r:+')

拜托，谁能帮帮我？谢谢。

【参考方案1】：

在您的代码中：drop_p = P1-P2 和 L = 63.068，因此除非 P2 是一个向量，否则您的图表中只会出现一个红色 +。像这样（P2 = 1）：

现在，solve 行返回错误，因为它应该在要解决的变量上带有''：

solve( (formule*better_express)- func1*log(P2+ exprs1/P1 + exprs1)^2 + L == 0, 'P2')

但这不会影响结果图，因为solve 输出没有分配给任何变量。