ESPhome filters: delta as ">" or as ">="

kouny · April 15, 2024, 9:13am

From the docs I assume that delta applies a “greater than”, since they explain:

If a number is specified, it will be used as the absolute difference required. For example if the filter were configured with a value of 2 and the last value passed through was 10, only values greater than 12 or less than 8 would be passed through.

Not “greater or equal”, just “greater”.

But in the source code I see:

github.com

esphome/esphome/blob/6876c65edada3710687260c91302ccfa432d4f08/esphome/components/sensor/filter.cpp#L348


      
            if (std::isnan(value)) {
              if (std::isnan(this->last_value_)) {
                return {};
              } else {
                if (this->percentage_mode_) {
                  this->current_delta_ = fabsf(value * this->delta_);
                }
                return this->last_value_ = value;
              }
            }
            if (std::isnan(this->last_value_) || fabsf(value - this->last_value_) >= this->current_delta_) {
              if (this->percentage_mode_) {
                this->current_delta_ = fabsf(value * this->delta_);
              }
              return this->last_value_ = value;
            }
            return {};
          }
          
          // OrFilter
          OrFilter::OrFilter(std::vector<Filter *> filters) : filters_(std::move(filters)), phi_(this) {}

and that’s (based on my limited knowledge of C++) a “greater than or equal to”.

Should the documentation be corrected, or the source code?

I think the latter, since I could use delta: 0 to avoid publishing identical values. With “>=” I have to pick an arbitrary sufficiently small number to obtain the same results, which seems to be a hack when I could pick “0” without the “equal to”.

Is there any reason to use “>=”?

Mahko_Mahko · April 15, 2024, 11:10am

I read it the same as you.