by
Les May
If the image does not load automatically click this link to see it.*
DURING
the daily updates of the new cases and deaths due to Covid19
infection the speaker usually makes reference to one or more charts.
To the best of my knowledge the only person from the media who has
drawn attention to the fact that the charts are drawn with a ‘log
scale’.
Here the word ‘log’
is shorthand for the word ‘logarithmic’.
What this means is that each division on the vertical (left hand
side)
shows equal ratios.
So 100 is ten times more than 10, 1,000 is ten times more than 100,
10,000 is ten times more than 1,000, so these show as the same size
division on the scale.
This
has two advantages. The first is that small numbers of cases at the
start of the UK pandemic and large numbers as we have now and in the
foreseeable future can be shown on the same scale. More importantly
when cases (or deaths) are plotted on a log scale the slope
of the line can be used to calculate the rate of increase, or to put
it another way, the number of days it takes for the number of cases
(or deaths) to double. The steeper the line the shorter the time for
the number to double.
In
the chart the figures for cases and deaths are plotted with a thicker
line; blue for cases, orange for deaths. The same colours have been
shown to plot the thin lines which show the slope
early in the pandemic and more recently.
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* What
is clear is that up to 17 March the daily
rate
of increase in the number of cases was greater than it has been in
the period 27 March to 6 April and the rate of increase in the number
of deaths was lower in the period 20 March to 6 April than it was
before
20 March.
This
is good news but
the thick blue line will have to become more or less horizontal
before we will know if the ‘lockdown’
and ‘social
distancing’
measures have been effective.
The
image which appears at the head of this article is the situation as
it was on 5 April. Clicking on the image loads a larger version of
that image. To get the most up to date image of the data click on
the link below the image. Today 8 April this has been updated
to show the number of confirmed cases and deaths up to Tuesday 7
April.
As
you will see from the new image the slope of the curves in recent
days has begun to decrease which is further good news. It is a hint,
but only a hint, that the so called ‘lockdown’
and the social distancing are starting to have the desired effect of
reducing the infection rate.
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1 comment:
The image which appears at the head of this article is the situation as it was on 5 April. Clicking on the image loads a larger version of that image. To get the most up to date image of the data click on the link below the image. Today 8 April this has been updated to show the number of confirmed cases and deaths up to Tuesday 7 April.
As you will see from the new image the slope of the curves in recent days has begun to decrease which is further good news. It is a hint, but only a hint, that the so called ‘lockdown’ and the social distancing are starting to have the desired effect of reducing the infection rate.
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