How to write conditional statement/loop?

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Ranjan Kandasamy
Ranjan Kandasamy 2021-9-7
编辑： Jan 2021-9-10
I need to plot with an expression for V<0 and another expression for V>0.
clc
clear all
n = 1.02; %Ideality factor
A = 33.65; %Richardson constant
q = 1.602*10^-19; % electron charge
K = 1.38*10^-23; %Boltzmann constant
T = 300; % Absolute temperature
phi_b = 0.28; %Barrier Height
J_0 = A* (T* T)* exp((-q* phi_b)./(K* T));
V = linspace(0,2);
if V<0
J = -J_0;
else
J = J_0.* exp((q* V)./(n* K* T)).* (1 - (exp(-q* V)./(K* T)));
end
plot(V, log(J ./(1 - exp(-q* V)/(K *T))));

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采纳的回答

Jan
Jan 2021-9-7
For V = linspace(0, 2) there is no V < 0. But in general:
V = linspace(-2, 2);
J = J_0.* exp((q * V) ./ (n * K * T)) .* (1 - (exp(-q * V) ./ (K * T)));
J(V < 0) = -J_0;
  2 个评论
Jan
Jan 2021-9-7
编辑：Jan 2021-9-10
Of course it would work, but it is slower, less elegant and offers more chances for typos:
V = linspace(-2, 2, 100);
J = NaN(size(V)); % Pre-allocation
for k = 1:numel(V)
if V(k) < 0
J(k) = -J_0;
else
J(k) = J_0 * exp((q * V(k)) / (n * K * T)) * (1 - (exp(-q * V(k)) / (K * T)));
end
end
% Or slightly simpler:
V = linspace(-2, 2, 100);
J = repmat(-J_0, size(V)); % Pre-allocation with default value
for k = 1:numel(V)
if V(k) >= 0
J(k) = J_0 * exp((q * V(k)) / (n * K * T)) * (1 - (exp(-q * V(k)) / (K * T)));
end
end

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