how to write correct looping

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vaya putra
vaya putra 2020-7-8
评论： Walter Roberson 2020-7-8
hi all
i want to read file and which is some condition
for data 1-100 is read properly
but i am confused why is the value in line X>99 i can not get rigth value
A=readfile('pf_ext_pcs_1_ts_1_t_1_000000_0.vtu')';
C = A(10217:13618);
C=cellfun(@(x)sscanf(x,'%f'),C,'UniformOutput',false);
format long g
pf=cell2mat(C); % 0 represents fracture occurs
pf(pf<0.1) =10000; %
km=nan(1000,1); % total cell permeability multiplier
a=1;
for x=1:10000
km(x,:)=1/8*(pf(x,1)+pf(x+1,1)+pf(200+a,1)+pf(201+a,1)+pf(10201+a,1)+pf(10202+a,1)+pf(a+10401,1)+pf(a+10402,1));
if x>99 &&x<199
km(x,:)=1/8*(pf(201-a,1)+pf(202-a,1)+pf(302-a,1)+pf(303-a,1)+pf(10402-a,1)+pf(10403-a,1)+pf(10503-a,1)+pf(10504-a,1));
elseif x > 199
km(x,:)=1/8*(pf(302-a,1)+pf(303-a,1)+pf(403-a,1)+pf(404-a,1)+pf(10503-a,1)+pf(10504-a,1)+pf(10604-a,1)+pf(10605-a,1));
elseif x > 299
km(x,:)=1/8*(pf(403-a,1)+pf(404-a,1)+pf(504-a,1)+pf(505-a,1)+pf(10604-a,1)+pf(10605-a,1)+pf(10705-a,1)+pf(10706-a,1));

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采纳的回答

Florian
Florian 2020-7-8
for x=1:10000
if x<=99
km(x,:)=1/8*(pf(x,1)+pf(x+1,1)+pf(200+a,1)+pf(201+a,1)+pf(10201+a,1)+pf(10202+a,1)+pf(a+10401,1)+pf(a+10402,1));
elseif x>99 && x<=199
km(x,:)=1/8*(pf(201-a,1)+pf(202-a,1)+pf(302-a,1)+pf(303-a,1)+pf(10402-a,1)+pf(10403-a,1)+pf(10503-a,1)+pf(10504-a,1));
elseif x>199 && x<=299
km(x,:)=1/8*(pf(302-a,1)+pf(303-a,1)+pf(403-a,1)+pf(404-a,1)+pf(10503-a,1)+pf(10504-a,1)+pf(10604-a,1)+pf(10605-a,1));
else
km(x,:)=1/8*(pf(403-a,1)+pf(404-a,1)+pf(504-a,1)+pf(505-a,1)+pf(10604-a,1)+pf(10605-a,1)+pf(10705-a,1)+pf(10706-a,1));
end
end
  1 个评论
Walter Roberson
Walter Roberson 2020-7-8
for x=1:10000
if x<=99
km(x,:)=1/8*(pf(x,1)+pf(x+1,1)+pf(200+a,1)+pf(201+a,1)+pf(10201+a,1)+pf(10202+a,1)+pf(a+10401,1)+pf(a+10402,1));
elseif x<=199
km(x,:)=1/8*(pf(201-a,1)+pf(202-a,1)+pf(302-a,1)+pf(303-a,1)+pf(10402-a,1)+pf(10403-a,1)+pf(10503-a,1)+pf(10504-a,1));
elseif x<=299
km(x,:)=1/8*(pf(302-a,1)+pf(303-a,1)+pf(403-a,1)+pf(404-a,1)+pf(10503-a,1)+pf(10504-a,1)+pf(10604-a,1)+pf(10605-a,1));
else
km(x,:)=1/8*(pf(403-a,1)+pf(404-a,1)+pf(504-a,1)+pf(505-a,1)+pf(10604-a,1)+pf(10605-a,1)+pf(10705-a,1)+pf(10706-a,1));
end
end
You had to fail x<=99 to reach the first elseif . There are several ways to fail x<=99:
  1. x is non-scalar and has a mix of values. However, in a for x=1:10000 you can be sure that x will be numeric scalar
  2. x is nan, because comparing nan to anything is false, including nan == nan is false as is nan ~= nan. But we are in a for x = integer vector loop, so we know x will not be nan
  3. x <= 99 fails because x is a numeric scalar that is > 99
We can rule out the first two cases by context, leaving x > 99 . So the first elseif will only be reached if x > 99. And that being the case, it is not productive to test x>99 in the elseif: if it were false, then we could not have reached the elseif (under the pre-condition of integer scalar for loop)

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