An estimation device according to an aspect of the present invention includes an estimator and a selector. The estimator, for each of a plurality of times, estimates a probability density distribution of a parameter representing a state of a diagnosis object, based on a measurement value of the diagnosis object, the measurement value being measured up to each of the times. The selector selects one or more probability density distributions meeting a predetermined condition relating to the probability density distribution.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A diagnostic device, comprising: an estimator, for each of a plurality of times, estimating a probability density distribution of a parameter representing a state of a diagnosis object, based on a measurement value of the diagnosis object, the measurement value being measured up to each of the times; and a selector selecting one or more probability density distributions meeting a predetermined condition relating to the probability density distribution. 2. The diagnostic device according to claim 1, further comprising a estimated probability density distribution processor adding an index to the probability density distribution for each of the times, the probability density distribution being estimated by the estimator, wherein the selector selects one or more probability density distributions based on the index. 3. The diagnostic device according to claim 1, wherein the estimator estimates a new probability density distribution based on a probability density distribution at a first time and a likelihood calculated based on a measurement value after the first time. 4. The diagnostic device according to claim 1, wherein the estimator estimates the probability density distribution using a particle filter. 5. The diagnostic device according to claim 1, wherein the condition is that a difference between the probability density distribution selected by the selector and the probability density distribution calculated by the estimator is not larger than a predetermined threshold value. 6. The diagnostic device according to claim 5, wherein the difference is calculated based on Kullback-Leibler divergence or extended Kullback-Leibler divergence. 7. The diagnostic device according to claim 1, further comprising an output circuit outputting at least any one of the probability density distributions estimated by the estimator and the probability density distributions selected by the selector. 8. The diagnostic device according to claim 2, further comprising an output circuit outputting at least any one of the probability density distributions estimated by the estimator and the probability density distributions selected by the selector; and the index includes a date and a time of measurement of the measurement value or a content of the measurement value; and information output by the output circuit includes the index. 9. The diagnostic device according to claim 7, further comprising an input circuit receiving an input from a user, wherein: based on a search condition from the input circuit, the selector selects one or more probability density distributions meeting the search condition; and the output circuit outputs at least any one of the selected probability density distributions. 10. An estimation method for making a computer perform: estimating, for each of a plurality of times, a probability density distribution of a parameter representing a state of a diagnosis object based on a measurement value of the diagnosis object, the measurement value being measured up to each of the times; and selecting one or more probability density distributions meeting a predetermined condition relating to the probability density distribution. 11. A non-transitory computer readable medium having a computer program stored therein which causes a computer when executed by the computer, to perform processes comprising: estimating, for each of a plurality of times, a probability density distribution of a parameter representing a state of a diagnosis object based on a measurement value of the diagnosis object, the measurement value being measured up to each of the times; and selecting one or more probability density distributions meeting a predetermined condition relating to the probability density distribution. 12. A diagnostic system comprising a diagnosis object, a first communication device, a second communication device and a third communication device, wherein: the first communication device sends a measurement value of the diagnosis object to the second communication device; the second communication device includes an estimator, for each of a plurality of times, estimating a probability density distribution of a parameter representing a state of the diagnosis object, based on the measurement value of the diagnosis object, the measurement value being measured up to each of the times, a selector selecting one or more probability density distributions meeting a predetermined condition relating to the probability density distribution, and an output circuit that outputting at least any one of the probability density distributions estimated by the estimator and the probability density distributions selected by the selector; and the third communication device receives the output from the output circuit.