Unrecognized Variable when running a graph

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Kailin Johnsson 2020-11-10

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https://ww2.mathworks.cn/matlabcentral/answers/643615-unrecognized-variable-when-running-a-graph

评论： Kailin Johnsson 2020-11-10

Hello,

I am tyring to run a very simple code, however every time I use the a variable in this locaiton on MatLab, it says the variable is not recognized despite being defined... any suggestions? When I run the code without multiple formulas input it works fine. Thanks!

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Answer 1

David Hill 2020-11-10

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https://ww2.mathworks.cn/matlabcentral/answers/643615-unrecognized-variable-when-running-a-graph#answer_540560

Move your plot function below the line (31) where variable E is defined.

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Kailin Johnsson 2020-11-10

编辑：Walter Roberson 2020-11-10

在 MATLAB Online 中打开

%Malthusian Growth Model
% Time interval
% t = (1790:10:2010)';
 
% Previous population
Pn = [2.91 3.929 5.308 7.239 9.638 12.866 17.069 23.191 31.443 39.818 50.189 62.947 76.212 92.228 106.021 122.775 132.164 150.697 179.323 203.302 226.545 248.709 281.421]';
 
% Growth Rate Assumption
R = (0.349+1)';
 
%Malthusian Model
E = (Pn*R)';
 
% Discrete Logistic Model
% Parameter and intial condtions
clear
clc
 
r= (0.349);
% Carrying Capactiy 
M= 451.7; 
 
 
X0= 3.929;
p= [2.913 3.929 5.308 7.239 9.638 12.866 17.069 23.191 39.818 50.189 62.947 76.212 92.228 106.021 122.775 132.164 150.697 179.323 203.302 226.545 248.709 281.421 308.745]';
 
% For loop to generate seqeunce terms
for i=1:length(p)
    F(i)=p(i)+r*p(i)*(1-p(i)/M)';
end
 
tBegin = 1790;     % time begin
tEnd = 2010;      % time end
 
 
% Time Interval
% a=(1790:10:2010)';
% Population
b= [3.929 5.308 7.239 9.638 12.866 17.069 23.191 31.443 39.818 50.189 62.947 76.212 92.228 106.021 122.775 132.164 150.697 179.323 203.302 226.545 248.709 281.421 308.745]';
 
Data = b;
 
Labels2 = [1790:10:1860]';
Labels = [1790:10:2010]';
 
% Plot all models 1790-2010
figure
plot(Labels,Data,'k-*',Labels,E,'b-*',Labels,F,'m-*')
title('Comparison of Models of US Census Data, 1790-2010')
legend('Data','Malthusian','Discrete Logistic')
axis([1780 2020 0 3.5e+8])
hold on

David Hill 2020-11-10

在 MATLAB Online 中打开

Your were clearing E!

M= 451.7; 
 
 
X0= 3.929;
p= [2.913 3.929 5.308 7.239 9.638 12.866 17.069 23.191 39.818 50.189 62.947 76.212 92.228 106.021 122.775 132.164 150.697 179.323 203.302 226.545 248.709 281.421 308.745]';
 
% For loop to generate seqeunce terms
for i=1:length(p)
    F(i)=p(i)+r*p(i)*(1-p(i)/M)';
end
 
tBegin = 1790;     % time begin
tEnd = 2010;      % time end
 
 
% Time Interval
% a=(1790:10:2010)';
% Population
b= [3.929 5.308 7.239 9.638 12.866 17.069 23.191 31.443 39.818 50.189 62.947 76.212 92.228 106.021 122.775 132.164 150.697 179.323 203.302 226.545 248.709 281.421 308.745]';
 
Data = b;
Labels = [1790:10:2010]';
 
% Plot all models 1790-2010
plot(Labels,Data,'k-*',Labels,E,'b-*',Labels,F,'m-*');
title('Comparison of Models of US Census Data, 1790-2010');
legend('Data','Malthusian','Discrete Logistic');
axis([1780 2020 0 500]);%changed axis to more appropriate