Finding "local maximas" but ignore value less than 20% of highest one

Question

I'm trying to create a function to find a "local maximas" in every row of my data but ignore if they are not atleast 20% of the "highest" maximum in a row.

Function which I use to find a local maximas:

which(diff(sign(diff(Gene name)))==-2)+1

but I would like to modify it and set pick only if the other maxima is atleast 20% of the highest value.

That's my data:

Name     Mo   Tue   Wen   Thu   Fr   Sat   Sun   
Mark     0     32    53    11    0    33    52   
Ettin    22    51    31    0     0    1      0
Gerard   36    0     13    0    111   33     0   
Marcus   0     44    31    10    0    2      0     

That's an output I got with my function:

Name     Mo   Tue   Wen   Thu   Fr   Sat   Sun   
Mark     0     0     1     0     0    0     1   ## Two local maximas
Ettin    0     1     0     0     0    1     0   ## Two local maximas (Should be one!)
Gerard   1     0     1     0     1    0     0   ## Three local maximas (Should be two!)
Marcus   0     1     0     0     0    1     0   ## Two local maximas (Should be one!)

For 3 rows the output isn't correct because the values in cells (Ettin,Sat) & (Gerard, Wen) & (Marcus, Sat) are not even close to atleast 20% of the highest value.

That's what I expect to get with new function:

Name     Mo   Tue   Wen   Thu   Fr   Sat   Sun   
Mark     0     0     1     0     0    0     1   
Ettin    0     1     0     0     0    0     0   
Gerard   1     0     0     0     1    0     0   
Marcus   0     1     0     0     0    0     0  

Is it possible to write such function ?

    if(master[j,i]>master[j,i-1]) {
      if(master[j,i] > 0.2*max(master [j,])) {
        mas_max[j,i] <- 1 ## Setting maxima
        mas_max[j,i-1] <- 0 ## Removing potential maxima before
 }
}

That's a loop I created but it is not the best way to get desired results.

Answer 1

If your local maxima are at

ind <- which(diff(sign(diff(GeneName)))==-2)+1

then you can get the indices of the thresholds that are no less than 20% of the highest by

ind[GeneName[ind] >= 0.2 * max(GeneName[ind])]

Also, note that ==-2 won't spot local maxima that are part of a plateau, for instance it won't spot c(0,10,10,0) - not sure if that's an issue, but thought it best to point that out.