population growth for this problem matlab

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marie 2013-2-20

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https://ww2.mathworks.cn/matlabcentral/answers/64326-population-growth-for-this-problem-matlab

编辑： per isakson 2017-8-22

The population of a certain country is 50 million and is expected to double in 20 years. Calculate the population 5, 10, and 15 years from now by defining a vector t with 3 elements and using element-by-element calculations. Population growth can be modeled by the equation p=p02^t/d where P is the population at time t, 0 P is the population at t = 0, and d is the doubling time.

so the equation is p=p02^t/d

I have d=ln(2)/20=0.035 then ln(2)/0.035

p=50000000*exp(d/t)

is that righ?

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Youssef Khmou 2013-2-21

编辑：Youssef Khmou 2013-2-21

the population is 50 e+6 now and expected to double in 20 years, so 100 millions next 20 years ? "double" like x2 ? anyway it means increasing but your last equation is decreasing, at least change the last eq to : exp(t/d) .

Subrata Paul 2017-8-22

编辑：per isakson 2017-8-22

在 MATLAB Online 中打开

Try this...

%Taking the inputs
p0 = input('Enter the population at time(0): ');
d = input('Enter time in which population will be double: ');
%Have to calculate at 5,10,15 years
t = [5 10 15];
l = length(t);
%Population 
p = ones(1,3)
for i = 1:l
    temp = pow2( t(i) / d);
    x(i) = floor( p0 * temp);
end
%Output
'The populations at 5,10 and 15 years are gradulally ' 
x
%Drawing graph
plot(t,x,'p-b');
xlabel('Years(t)'); ylabel('Population');
title('Population at different years');