I have a time series of values and corresponding dates, continous but not with equal interval. I have created the graph and chosen the "date" column as x-axis but it is not registered. I have set the cell-type as "date", but on the x axis it just put the line number correspondig to the value. Even the correct values are displayed when I open the "select data source", but they do not show on the x axis.
It appears you are using the wrong type of graph for what you want. It is treating the values as categories rather than a continuous variable. Use a scatter (XY) chart. You will need to format the X axis with a date format.
On your chart, double click on the values of your x-axis and it will open up a new window - Format axis
Format axis:
Then you can check the format to show the dates. Might be a formatting thing as I tried and it automatically showed the dates on the x axis.
In the "Format Axis" dialog, select "Number". This will enable you to select the appropriate display format, which is likely set to "General" if you're seeing raw integer values vice "dates".
In my experience, some dates where not properly filled in. The cells where well formatted, the date format being applied to all the column at once, and the dates were being displayed properly as yyyy-mm-dd, but they had to be filled in as dd/mm/yyyy and some where instead filled in as yyyy-mm-dd. Changing the improper yyyy-mm-dd dates to dd/mm/yyyy fixed my issue.
On a similar type of graph of mine I see the following:
In the data, if I select Sort & Filter > Sort, the dialogue shows "Data has Headers" and the related data for those headers is selected.
On the graph if I select the curve, right-click and select "Select Data", the columns of data selected for the graph line are highlighted with a dotted border and a dialogue "Select data source" shows the horizontal axis labels.
