How to include vectors in IF statement?

Question

Mohammed Lamine Mekhalfia 2022-6-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1736240-how-to-include-vectors-in-if-statement

编辑： Torsten 2022-6-8

采纳的回答： Mohammed Lamine Mekhalfia

在 MATLAB Online 中打开

Dear.

in my code below I am trying to plot an output.

This output is related to a vector S so , the output would equal 1 if the value of time t equals one (1) of the value of the vector S else the output = 0

how to integrate this if statement wit the fact that S is a vector

I tried a lot

Instead of the (3) I need to make an index

My code:

clear all
omega=1000 %rotation frequency (rpm)
omega_rad=(omega*2*pi)/60 %rotation frequency (rad/s)
TRot=(360*(pi/180))/omega_rad %Time of one rotation
Holes=15 %Number of holes in Cylinder
Pressure_In1=0 %Pressure Amplitude in Bar
Pressure_In2=1 %Pressure Amplitude in Bar
alpha=360/Holes %angles between holes (degree)
beta=11.20 %angles swept by 1 hole (degree)
alpha_rad=alpha*(pi/180) %angles between holes (rad)
beta_rad=beta*(pi/180) %angles swept by 1 hole (rad)
k=TRot/100 %timestep
h=1
f=1
for N=1:1:Holes
s= TRot*(N*alpha)/360
S(f)=s
f=f+1
end
for time=0:k:TRot
if (time>(S(3)-0.002))&&(time<(S(3)+0.002))
    Press_out=Pressure_In2
else
    Press_out=Pressure_In1
end
Press(h)=Press_out
t(h)=time
h=h+1
  
end
plot(t,Press)

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Walter Roberson 2022-6-8

在 MATLAB Online 中打开

if (time>(S(f)-0.002))&&(time<(S(f)+0.002))

is that what you mean?

Mohammed Lamine Mekhalfia 2022-6-8

@Walter Roberson yes but this does not work

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Answer 1

Mohammed Lamine Mekhalfia 2022-6-8

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@Bhargava Hurulagere Sridharamurthy Thanks for the feedback

what my question mean:

check time if it is equal to a value there in vector S and based on that choose the output at that value

for example at time equal 0.075 go to the vector S and see if this condition is true

The condition (S(f) -0.0001 )< time < (S(f) +0.0001 ). the vector S contains 15 values so it need to check for all of it.

if this is true then pressure output = 1

if not pressure output = 0

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Torsten 2022-6-8

编辑：Torsten 2022-6-8

在 MATLAB Online 中打开

if the condition should be true for all elements of the vector S:

if abs(S-time) < 0.0001  
    Press_out=Pressure_In2
else
    Press_out=Pressure_In1
end

if the condition should be true for at least one element of the vector S:

if any(abs(S-time) < 0.0001)
    Press_out=Pressure_In2
else
    Press_out=Pressure_In1
end

if you want to check the condition for all elements of S separately:

Press_out = Pressure_In1*ones(size(S));
idx = abs(S-time) < 0.0001;
Press_out(idx) = Pressure_In2;

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Answer 2

Bhargava Hurulagere Sridharamurthy 2022-6-8

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Hello Mohammed,

I understand that you want to find whether a given value exists in vector or not. If Exists, access the value by returned index and do further calculations.

You can perform this task using the MATLAB function 'ismember'

Refer to the below page for usage and syntax of MATLAB function 'ismember':

https://www.mathworks.com/help/matlab/ref/double.ismember.html

I hope that the information provided helps in resolving your query.

Thanks,

Bhargava,