why If statement is not work?

eq1 have at each nf the values 0.186170065500000 0.336133515500000 0.486096965500000 0.636060415500000 0.786023865500000 0.935987315500000 1.08595076550000

i want to plot out1 when eq1 >1so, out1 should be calculated at 1.08595076550000

eq1=((bwf*nf)./wi)+((bwm*nm1)./wi);
out1=(bwf*nf)./wi;
plot (eq1);
hold on

if all(eq1 >=1)
    out1=(bwf*nf)./wi;

plot (out1);

end

[Adam]

To answer the question in the title, read the logic of your if statement.

if all( eq1 >= 1 )

i.e. it will only evaluate to true if all the values in eq1 are greater than or equal to 1. The result is a scalar logical, as needed generally for an if statement, but it isn't capturing what you want.

Answer 1

[madhan ravi]

Read https://www.mathworks.com/matlabcentral/answers/428770-why-isn-t-matlab-counting-this-as-equal-to-1#answer_345891 and https://www.mathworks.com/matlabcentral/answers/428577-very-odd-error-with-simple-multiplication-ok-not-so-odd#answer_345716 to know how floating numbers are compared

[maryhan mohamed]

it works now

but,

nf 1:7

so eq1 will be >1 at nf=7 only

when out1 is calculated by the above code it calculate all nf 1:7 not nf=7

[madhan ravi]

Did you read the first link?

[maryhan mohamed]

yes, i got my floating point problem

but

 
nf = 1, 2,3,4,5,6,7

and

eq1 will be >1 at nf=7

please, i want to calculate the out1 when eq1 >1 at nf =7

 out1=(bwf*nf)./wi;

my code give me result for out1 at each nf not at nf =7

eq1=((bwf*nf)./wi)+((bwm*nm1)./wi);
out1=(bwf*nf)./wi;
plot (eq1);
hold on

if sum(eq1)>=1
    out1=(bwf*nf)/wi;

plot (out1);

end

[madhan ravi]

if abs(eq1-1)>1e-4 %set tolerance by the way you didn't read the links I suggested 

[maryhan mohamed]

from the shown code,

eq1=((bwf*nf)./wi)+((bwm*nm1)./wi);
out1=(bwf*nf)./wi;
plot (eq1);
hold on
if abs(eq1-1)>1e-4
    out1=(bwf*nf)/wi;
plot (out1);
end

the output will be

eq1=0.186170065500000	0.336133515500000	0.486096965500000	0.636060415500000	0.786023865500000	0.935987315500000	1.08595076550000
out1=0.149963450000000	0.299926900000000	0.449890350000000	0.599853800000000	0.749817250000000	0.899780700000000	1.04974415000000

please,, what i want is to make out1 result = 1.04974415000000 only % nf=7 at eq1=1.08595076550000 which is greater than 1.

thanks for ur helping,

[madhan ravi]

bwf , wi?

[maryhan mohamed]

wi=10000000;
nf=1:7;
nm1=1;
bwf=1499634.50;
bwm=362066.155;

[madhan ravi]

wi=10000000;
nf=1:7;
nm1=1;
bwf=1499634.50;
bwm=362066.155;
eq1=[0.186170065500000  0.336133515500000   0.486096965500000   0.636060415500000   0.786023865500000   0.935987315500000   1.08595076550000];
idx=abs(eq1-0)>1
result=(bwf*nf)/wi;
result=result(idx)

Answer 2

[Image Analyst]

The link about comparing equality of floating point numbers is good information, though it doesn't apply here since none of your eq1 numbers are expected to be exactly 1 - they're all clearly either more than or less than 1.

Your original code

wi=10000000;
nf=1:7;
nm1=1;
bwf=1499634.50;
bwm=362066.155;
eq1=((bwf*nf)./wi)+((bwm*nm1)./wi);
out1=(bwf*nf)./wi;
plot (eq1);
hold on
if all(eq1 >=1)
	out1=(bwf*nf)./wi;
	plot (out1);
end

did plot the first plot. It did not plot the second plot since not ALL elements of eq1 were more than 1. I believe you want masking, where you plot only those elements where eq1 > 1 and no others ("i want to plot out1 when eq1 >1"). To do that, see this corrected code:

wi=10000000;
nf=1:7;
nm1=1;
bwf=1499634.50;
bwm=362066.155;
eq1=((bwf*nf)./wi)+((bwm*nm1)./wi)
% Plot eq1.
plot (eq1, 'bo-');
xlabel('index', 'FontSize', 15);
ylabel('eq1', 'FontSize', 15);
grid on;
% Compute out1.
out1 = (bwf * nf) ./ wi % Note: same as
% Create a mask where only those where eq1 > 1 are true.
mask = eq1 > 1
% Plot only those where eq1 > 1 (where the mask is true).
hold on;
x = 1 : length(out1)
plot (x(mask), out1(mask), 'r*', 'MarkerSize',13, 'LineWidth', 2);
legend('eq1', 'out1', 'Location', 'north');

Your original eq1 (outside the if block) is plotted in blue while the points of out1, only where eq1 is greater than 1, are plotted in red.

[maryhan mohamed]

thanks alot for your help