how to change the number that decreases in the array element to the same number, for example 0 (zero)

hello everyone,

I have an array element value as in the following code and this number will keep decreasing to about 10e-6, there should be a lot up to (1x500) but I just gave a few examples with this,

is there an easy way to change it to the same number eg 0 (zero)?

So in general it is not if it is worth below 1, for example, then it is zero, not like that, but if it is worth decreasing

Thank you very much

a = [100.001469926008 0.0140073495254864 0.00452326089811489 0.00228582409151486 0.00157249586126199 0.00121055360392781 0.000988328854777707 0.000836846113296335 0.000726496714817108]
if %there are array elements that are keep decreasing
    %then everything changes to 0 so it remains (1x500) but everything is 0
end

Answer 1

[per isakson]

Is something like this what you are asking for?

%%
a = [100.001469926008 0.0140073495254864 0.00452326089811489        ...
    , 0.00228582409151486 0.00157249586126199 0.00121055360392781   ...
    , 0.000988328854777707 0.000836846113296335 0.000726496714817108 ];
%%
daff = diff(a);
ix = find( a<1, 1, 'first' );   % "worth below 1"
if all( daff(ix:end) < 0 )      % "keep decreasing"
    a(ix:end)=0;                % "changes to 0"
end

it returns

>> a
a =
  Columns 1 through 5
          100            0            0            0            0
  Columns 6 through 9
            0            0            0            0
            

Based on the comments below I think the best answer is:

%%
daff = diff(a);
if all( daff < 0 )  % "keep decreasing"     monotonically decreasing
    a(:) = 0;       % "changes to 0"        "(:)" is needed to replace ALL values by 0 
end 

[Naufal Arfani]

I am very grateful for your generosity @per isakson, but I want to ask a little more if then I want to make everything 0 even for 100, do I only need to delete the ones worth below 1 or what? Thank you very much. or maybe the example is this

%%
a = [100.001469926008 0.0140073495254864 0.00452326089811489        ...
    , 0.00228582409151486 0.00157249586126199 0.00121055360392781   ...
    , 0.000988328854777707 0.000836846113296335 0.000726496714817108 ];
%%
daff = diff(a);
if all( daff < 0 )      % "keep decreasing"
    a = 0;                % "changes to 0"
end

[Naufal Arfani]

I'm trying like this so that it goes zero and doesn't get into findpeaks but why is it still an error? @per isakson

function [dist,peak2,locs2] = fcn(u)

daff = diff(u);
ix = find( u<1, 1, 'first' );   % "worth below 1"
if all( daff(ix:end) < 0 )      % "keep decreasing"
    u(ix:end)=0;                % "changes to 0"
end

locs = zeros(size(u));
pks = zeros(size(u));

if u ~= 0
    [pks,locs] = findpeaks(u);
else
    locs(size(u))= 0;
    pks(size(u)) = 0;
end

a = locs(2)-locs(1);
b = pks(1);
c = locs(1);
dist = a;
peak2 = b;
locs2 = c;

and the error is

[Naufal Arfani]

I'm sorry even though your answer is already very good @per isakson

[per isakson]

Your example won't run, because ix isn't defined. (This comment is in response to your first version of your first comment.)

%%
daff = diff(a);
ix = find( a<1, 1, 'first' );   % "worth below 1"
if all( daff(ix:end) < 0 )      % "keep decreasing"
    a(1:end)=0;                 % "changes to 0"    from the first element
end % ^

or rather

%%
daff = diff(a);
if all( daff < 0 )  % "keep decreasing" decreases from first to last element
    a(:) = 0;       % "changes to 0"    "(:)" is needed to replace ALL values by 0 
end 

[Naufal Arfani]

sorry when I tried to use yours from the second one I found that the array value was (1-1) with an error like this

then I tried to add it to be the same as the one above but he said there was still one missing what then needed to be added again please help me a little more

function [dist,peak2,locs2] = fcn(u)

locs = zeros(size(u));
pks = zeros(size(u));

daff = diff(u);
if all( daff(size(u)) < 0 )      % "keep decreasing" decreases from first to last element
    u(:) = 0;           % "changes to 0"    replace all values by 0 
end  


if u ~= 0
    [pks,locs] = findpeaks(u);
else
    locs(size(u))= 0;
    pks(size(u)) = 0;
end

a = locs(2)-locs(1);
b = pks(1);
c = locs(1);
dist = a;
peak2 = b;
locs2 = c;

the error is like this

so that I think there is still one more, I beg you very much for your help. If it works, I will wish you all the goodness @per isakson

[Naufal Arfani]

I also don't understand why the array element is 1-1 even though the time in the example above is coded for 1-9 @per isakson

[Naufal Arfani]

is it possible that there is less one value that does not decrease in value @per isakson

[per isakson]

In response to your second comment. (What has Simulink to do with this. I use an old time m-file.)

>> [dist,peak2,locs2] = fcn(a)
dist =
     0
peak2 =
     0
locs2 =
     0

where

function [dist,peak2,locs2] = fcn(u)
    
    daff = diff(u);
    if all( daff < 0 )      % "keep decreasing"
        u(:) = 0;           % "changes to 0"
    end
    
    locs = zeros(size(u));
    pks = zeros(size(u));
    
    if not( all( u == 0 ) ) % you tested only on the first element of u                
        [pks,locs] = findpeaks(u);
    else
        locs(size(u))= 0;
        pks(size(u)) = 0;
    end
    
    a = locs(2)-locs(1);
    b = pks(1);
    c = locs(1);
    dist = a;
    peak2 = b;
    locs2 = c;
end

[Naufal Arfani]

My code at the beginning is a good code that can detect peaks and locs well but when the input condition continues to decline so there is no peak so findpeaks is useless so I want to create a condition where everything whose value decreases becomes 0 but keeps the array condition is (1x501) so locs (2) etc. can have a value of 0 @per isakson

[per isakson]

"error which is an array of (1-1)," What array? See TUTORIAL: how to ask a question (on Answers) and get a fast answer

I cannot run your Simulink model on R2018b.

daff is one element shorter than u (see help on diff). I never proposed size(u) in all(daff(size(u)).

[Naufal Arfani]

I have changed my simulink to r2018b I hope you want to see it first so you understand what I mean @per isakson

I will also pay attention to the tutorial you submit

[Naufal Arfani]

I see there are indeed some bad things I do like sending my simulink, but I just mean for you to check if then if something goes wrong with my work because some of the suggestions you have given are actually very good but I don't know why it's still not worked too @per isakson

therefore I apologize for breaking a few things there because I have been asking this for a long time about 2 weeks ago

because maybe what is in Matlab is different from what is in Simulink

[per isakson]

"I have been asking this for a long time about 2 weeks ago"

• how to change the number that decreases in the array element to the same number, for example 0 (zero) (this question) 1 answer, 12 comments
• findpeaks [pks, locs] cannot detect NaN 1 answer, 9 comments (Walter Roberson explained why the statement, if u ~= 0, is wrong in the context. Nevertheless, it appears in a code of one of your comments of this question.)
• how to make nan turn into 0 in array 0 answers, 22 comments
• and a couple of more questions, which are on related problems

Several people have put a fair amount of effort into helping you. They haven't contributed to answer this question. I guess, you lost them.

"because maybe what is in Matlab is different from what is in Simulink"

Communication is difficult. What does this paragraph say?

"have changed my simulink to r2018b"

I've run your model and browsed the diagnostics. It's above my head to debug this model.

See my addendum to the answer.

[Naufal Arfani]

okay, thank you very much for all the help. I'm sorry for always asking and troubling you @per isakson